Dissertations / Theses: 'Geomagnetic storm'

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Davidson, Nigel Charles. "The analysis of geomagnetic storm-time variations." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/13577.

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The earth is bathed in an ever changing magnetic environment due to fluctuations in the solar wind. The external field induces currents within the earth which cause a secondary internal field. The ratio of internal to external parts of the magnetic potential is known as the response and may be derived from measurements of the field at the surface. The response of the earth is dependent on the spatial form of the field and distribution of conductivity within the earth. The analysis of numerous geomagnetic storms, large disturbances in the field surrounding the whole earth, is presented with the aim of determining a reliable response function which enables an estimate to be made of the average conductivity of the upper mantle. The compilation of a database of geomagnetic storms was a major part of the work. All the suitable storm events were selected between 1957 and 1982 to give 44 storms. The entire set of hourly values were checked for errors and corrections made where necessary. Where data were missing their values were interpolated using information from nearby observatories. The lower the frequency of external magnetic variations the deeper the penetration into the earth. The frequency content of geomagnetic storms allows depths approaching 1500km to be investigated. The observations of magnetic field were Fourier transformed and attention focussed on the Fourier coefficients of the lowest frequencies, 0.03 to 1 cycle per day. From Spherical Harmonic Analysis in the frequency domain it was found that a pure P1o spherical harmonic model is acceptable for the spatial form of the field at the frequencies of most interest. Thus the source is assumed to be a simple ring current in common with most of the previous research. The Fourier coefficients of the X and Z magnetic components were then fitted to the appropriate P1o model which allows the separate internal and external parts to be evaluated. A robust method, to reduce the influence of anomalous values, was used for determining the optimum fit to the Fourier coefficients. The technique was assessed by examining the distribution of residuals.

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Vaishnav, Rajesh Ishwardas, and Christoph Jacobi. "Correction to: Ionospheric response to the 25 - 26 August 2018 intense geomagnetic storm." Universität Leipzig, 2020. https://ul.qucosa.de/id/qucosa%3A74122.

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The thermosphere-ionosphere regions are mainly controlled by the solar, but also by geomagnetic activity. In this case study, the Earth’s ionospheric response to the 25-26 August 2018 intense geomagnetic storm is investigated using the International GNSS System (IGS) Total Electron Content (TEC) observations. During this major storm, the minimum disturbance storm time (Dst) index reached -174 nT. We use observations and model simulations to analyse the ionospheric response during the initial phase and the main phase of the magnetic storm. A significant difference between storm day and quiet day TEC is observed. The O/N2 ratio observed from the GUVI instrument onboard the TIMED satellite is used to analyse the storm effect. The result shows a clear depletion of the O/N2 ratio in the high latitude region, and an enhancement in the low latitude region during the main phase of the storm. Furthermore, the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model simulations were used. The results suggest that the CTIPe model can capture the ionospheric variations during storms. Die Regionen der Ionosphären und Thermosphäre werden hauptsächlich von der Sonne sowie auch von geomagnetische Aktivität beeinflusst. In dieser Fallstudie wurde die ionosphärische Reaktion der Erde auf den starken geomagnetischen Sturm vom 25./26. August 2018 unter Verwendung der Gesamtelektronengehaltsdaten (Total Electron Content, TEC) vom Internationalen GNSS Service untersucht. Während dieses großen Sturms wurde ein ”Disturbance Storm Time Index” Dst von -174 nT erreicht. Beobachtungen und Modellsimulationen wurden verwendet, um die ionosphärische Reaktion während der Anfangsphase und der Hauptphase des magnetischen Sturms zu untersuchen. Ein signifikanter Unterschied zwischen TEC während eines Sturmtages und eines ruhigen Tages wurde beobachtet. Das vom GUVI-Instrument an Bord des TIMED-Satelliten beobachtete O/N2 -Verhältnis wurde verwendet, um den Sturmeffekt weiter zu untersuchen. Das Ergebnis zeigt eine deutliche Abnahme/Zunahme des O/N2 Verhältnis in hohen/niedrigen Breiten während der Hauptphase des Sturms. Darüber hinaus wurde das Coupled Thermosphere Ionosphere Plasmasphere ectrodynamics (CTIPe) Modell verwendet. Die Ergebnisse legen nahe, dass das CTIPe-Modell die ionosphärischen Schwankungen während eines Sturms erfassen kann.

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3

Xu, Zhonghua. "Study of Geomagnetic Disturbances and Ring Current Variability During Storm and Quiet Times Using Wavelet Analysis and Ground-based Magnetic Data from Multiple Stations." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/984.

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The magnetosphere-ionosphere contains a number of current systems. These currents vary on a wide range of spatial and temporal scales and physically couple with each other. To study the complicated behaviors of these coupled current systems, the ground-based magnetometer has been a useful tool, but the recorded magnetometer data are always multi-scaled and intermittent due to the nature of these current systems. To distinguish these geomagnetic effects with multiple temporal and frequency scales, the wavelet analysis technique is especially suitable because of its special abilities of presenting information in both temporal and frequency domains. In this dissertation, the geomagnetic disturbances and the ring current variability during storm and quiet times are studied by using wavelet analysis and ground-based magnetic data from multiple stations. The first part of this dis- sertation investigates the strengths of applying the wavelet procedure to geomagnetic data for ring current study during storm and quiet periods. The second part of this dissertation characterizes the geomagnetic effects caused by symmetric and asymmetric components of ring currents during storm and quiet times by applying wavelet analysis to geomagnetic data from multiple stations. The third part of this dissertation studies the spatial variabil- ity of the symmetric ring current by applying the wavelet analysis technique to multiple components of magnetic data from multiple stations. The results show the unique strengths of the wavelet method allow us to quantitatively distinguish the geomagnetic effects on ring current variations from other M-I current systems. The unique strengths of wavelet method also allow us to separate the magnetic effects of the symmetric ring current from those caused by the asymmetric ring current. Quantitative information of the spatial variability of the ring currents is essential for understanding the dynamics of the ring currents, as well as the magnetic storm processes. The techniques developed in this dissertation have potential values as space weather monitoring tools for satellite controls, power grids, com- munication systems, oil pipelines, and other high-tech systems that are vulnerable to the negative impacts of disruptive geomagnetic events.

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Chatterjee, Kausik. "The Development of Hydrodynamic and Kinetic Models for the Plasmasphere Refilling Problem Following a Geomagnetic Storm." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7364.

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The objective of this dissertation is the development of computer simulation-based models for the modeling of upper ionosphere, starting from the first principles. The models were validated by exact analytical benchmarks and are seen to be consistent with experimentally obtained results. This area of research has significant implications in the area of global communication. In addition, these models would lead to a better understanding of the physical processes taking place in the upper ionosphere.

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Matsuoka, Marcelo Tomio. "Influência de diferentes condições da ionosfera no posicionamento por ponto com GPS : avaliação na região brasileira." Presidente Prudente : [s.n.], 2007. http://hdl.handle.net/11449/100257.

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Orientador: Paulo de Oliveira Camargo Banca: João Francisco Galera Monico Banca: Márcio H. O. Aquino Banca: Inez Staciarini Batista Banca: Claudio Antonio Brunini Após a desativação da técnica SA, a ionosfera tornou-se a principal fonte de erro no posicionamento com GPS. O erro associado à ionosfera é diretamente proporcional ao conteúdo total de elétrons (TEC - Total Electron Content) presente ao longo do caminho da trajetória percorrida pelo sinal na ionosfera e inversamente proporcional ao quadrado da freqüência do sinal. O TEC, e conseqüentemente o erro devido à ionosfera, variam no tempo e no espaço e é influenciado por diversas variáveis, tais como: ciclo solar, época do ano, hora do dia, localização geográfica, atividade geomagnética, entre outros. A região brasileira é um dos locais que apresenta os maiores valores e variações espaciais do TEC e onde estão presentes diversas particularidades da ionosfera, tais como, a anomalia equatorial e o efeito da cintilação ionosférica. Desta forma, é importante a realização de pesquisas que visam estudar o comportamento do TEC, e conseqüentemente do erro devido à ionosfera no Brasil, que é um trabalho complexo devido aos diversos fatores que influenciam a variação do TEC, além das particularidades presentes na região brasileira. Estudos desta natureza podem auxiliar a comunidade geodésica brasileira, e demais usuários do GPS, no entendimento das limitações impostas pela ionosfera nas regiões de interesse. Devido à natureza dispersiva da ionosfera, o estudo do comportamento do TEC no Brasil pode ser realizado utilizando os dados GPS de receptores de dupla freqüência pertencentes à RBMC (Rede Brasileira de Monitoramento Contínuo). Adicionalmente, para uma melhor análise, pode-se também utilizar dados das estações da rede IGS (International GNSS Service) da América do Sul. In the SA absence, the ionosphere is the largest error source in GPS positioning. The error due to the ionosphere in the GPS observables depends on the signal frequency and Total Electron Content (TEC) in the ionospheric layer. The TEC varies regularly in time and space in relation to the sunspot number, the season, the local time, the geographic position, and others. The Brazilian region is one of the regions of the Earth that presents largest values and space variations of the TEC, being influenced by the equatorial anomaly of ionization and ionospheric scintillation. Therefore, it is important to study the TEC behavior in the Brazilian region. Due to the ionosphere dispersive nature, the TEC behavior in Brazil can be studied using GPS data from RBMC (Rede Brasileira de Monitoramento Contínuo - Brazilian Network for Continuous Monitoring of GPS). Additionally, GPS data from IGS (International GNSS Service) network of the South America can also be used in the experiments. Doutor

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6

Brückner, Marlen, Michael Lonardi, André Ehrlich, et al. "Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC): Overview of LIM Contributions." Leibniz-Institut für Troposphärenforschung, 2004. https://ul.qucosa.de/id/qucosa%3A74381.

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The thermosphere-ionosphere regions are mainly controlled by the solar, but also by geomagnetic activity. In this case study, the Earth’s ionospheric response to the 25-26 August 2018 intense geomagnetic storm is investigated using the International GNSS System (IGS) Total Electron Content (TEC) observations. During this major storm, the minimum disturbance storm time (Dst) index reached -174 nT. We use observations and model simulations to analyse the ionospheric response during the initial phase and the main phase of the magnetic storm. A significant difference between storm day and quiet day TEC is observed. The O/N2 ratio observed from the GUVI instrument onboard the TIMED satellite is used to analyse the storm effect. The result shows a clear depletion of the O/N2 ratio in the high latitude region, and an enhancement in the low latitude region during the main phase of the storm. Furthermore, the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model simulations were used. The results suggest that the CTIPe model can capture the ionospheric variations during storms.:Vaishnav, R., Jacobi, Ch.: Ionospheric response to the 25-26 August 2018 in- tense geomagnetic storm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Brückner, M., Lonardi, M., Ehrlich, A., Wendisch, M., Jäkel, E. Schäfer, M., Quaas, J., Kalesse, H.: Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC): Overview of LIM Contributions . . . . . 11 Seidel, C., Lochmann, M.: Statistische Analyse der jährlichenWindverteilung für energiemeteorologische Anwendungen an der Station Lindenberg . . . . . . 20 Jahresbericht des Instituts für Meteorologie 2019 . . . . . . . . . . . . . . . 34 Die Regionen der Ionosphären und Thermosphäre werden hauptsächlich von der Sonne sowie auch von geomagnetische Aktivität beeinflusst. In dieser Fallstudie wurde die ionosphärische Reaktion der Erde auf den starken geomagnetischen Sturm vom 25./26. August 2018 unter Verwendung der Gesamtelektronengehaltsdaten (Total Electron Content, TEC) vom Internationalen GNSS Service untersucht. Während dieses großen Sturms wurde ein ”Disturbance Storm Time Index” Dst von -174 nT erreicht. Beobachtungen und Modellsimulationen wurden verwendet, um die ionosphärische Reaktion während der Anfangsphase und der Hauptphase des magnetischen Sturms zu untersuchen. Ein signifikanter Unterschied zwischen TEC während eines Sturmtages und eines ruhigen Tages wurde beobachtet. Das vom GUVI-Instrument an Bord des TIMED-Satelliten beobachtete O/N2 -Verhältnis wurde verwendet, um den Sturmeffekt weiter zu untersuchen. Das Ergebnis zeigt eine deutliche Abnahme/Zunahme des O/N2 Verhältnis in hohen/niedrigen Breiten während der Hauptphase des Sturms. Darüber hinaus wurde das Coupled Thermosphere Ionosphere Plasmasphere ectrodynamics (CTIPe) Modell verwendet. Die Ergebnisse legen nahe, dass das CTIPe-Modell die ionosphärischen Schwankungen während eines Sturms erfassen kann.:Vaishnav, R., Jacobi, Ch.: Ionospheric response to the 25-26 August 2018 in- tense geomagnetic storm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Brückner, M., Lonardi, M., Ehrlich, A., Wendisch, M., Jäkel, E. Schäfer, M., Quaas, J., Kalesse, H.: Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC): Overview of LIM Contributions . . . . . 11 Seidel, C., Lochmann, M.: Statistische Analyse der jährlichenWindverteilung für energiemeteorologische Anwendungen an der Station Lindenberg . . . . . . 20 Jahresbericht des Instituts für Meteorologie 2019 . . . . . . . . . . . . . . . 34

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Van, de Heyde Valentino Patrick. "An Investigation of magnetic storm effects on total electron content over South Africa for selected periods in solar cycles 23 and 24." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/3997.

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>Magister Scientiae - MSc The development of regional ionospheric Total Electron Content (TEC) models has contributed to understanding the behavior of ionospheric parameters and the coupling of the ionosphere to space weather activities on both local and global scales. In the past several decades, the International Global Navigation Satellite Systems Service (GNSS) networks of dual frequency receiver data have been applied to develop global and regional models of ionospheric TEC. These models were mainly developed in the Northern Hemisphere where there are dense network of ground based GPS receivers for regional data coverage. Such efforts have been historically rare over the African region, and have only recently begun. This thesis reports the investigation of the effect of mid-latitude magnetic storms on TEC over South Africa for portions of Solar Cycles 23 and 24. The MAGIC package was used to estimate TEC over South Africa during Post Solar Maximum, Solar Minimum, and Post Solar Minimum periods. It is found that TEC is largely determined by the diurnal cycle of solar forcing and subsequent relaxation, but effects due to storms can be determined

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Salomoni, Christiane da Silva Santos. "GPS e ionosfera: estudo do comportamento do TEC e de sua influência no posicionamento com GPS na região brasileira em períodos de alta e baixa atividade solar." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15752.

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A ionosfera é uma das principais fontes de erro sistemático das observáveis GPS (Global Positioning System - Sistema de Posicionamento Global), pois, por ser um meio dispersivo, ela afeta a propagação de ondas eletromagnéticas, fazendo com que a modulação e a fase das ondas portadoras transmitidas pelos satélites GPS sofram, respectivamente, um retardo e um avanço, o que, por sua vez, provoca um erro na distância medida entre o satélite e o receptor. Esse erro é inversamente proporcional ao quadrado da freqüência do sinal e diretamente proporcional ao TEC (Total Electron Content - Conteúdo Total de Elétrons), ou seja, à densidade de elétrons presentes na ionosfera ao longo do caminho entre o satélite e a antena receptora. O TEC sofre variações regulares, cujo comportamento pode ser verificado ao longo do dia, ao longo das estações do ano e também ao longo de ciclos de aproximadamente onze anos (associados à ocorrência de manchas solares). Além dessas variações, eventos solares extremos (explosões solares, ejeções coronais de massa, entre outros) podem causar abruptas e significativas mudanças no comportamento do TEC, exercendo grande influência no posicionamento com GPS, principalmente com receptores de uma freqüência. No Brasil, o fator ionosfera é ainda mais relevante, pois essa região é afetada por fenômenos como a Anomalia Equatorial (AE), a Anomalia Magnética do Atlântico Sul (AMAS) e até mesmo pela ocorrência de irregularidades ionosféricas. Pretendendo aprofundar o entendimento da relação entre a ionosfera e o posicionamento com GPS na região brasileira, essa pesquisa analisou dados de TEC e dados de GPS em períodos de alta e baixa atividade solar, bem como em um período geomagneticamente perturbado. Os resultados demonstraram uma relação direta entre a redução do TEC, no período de baixa atividade solar, e a melhora no posicionamento com GPS. Essa melhora se traduziu, no posicionamento por ponto, por uma redução de 59% no erro planimétrico e 64% no erro altimétrico e, no posicionamento relativo, por uma redução de 65% no erro planimétrico e 63% no erro altimétrico. Já durante o período afetado por uma severa tempestade geomagnética verificou-se um comportamento completamente atípico da ionosfera, piorando muitos os resultados do posicionamento relativo, em horários e locais inesperados. The ionosphere is one of the main sources of systemathic error of the observable GPS (Global Positioning System) because as it is a dispersive environment it affects the propagation of electromagnetics waves making the modulation and the phase of signals transmitted by GPS sattelites go through, respectivelly, delay and advance which will cause an error in the measure of the distance between the sattelite and the receptor. This error is inversely proportional to the square of the frequency of the signal and directly proportional to the TEC (Total Electron Content), what means the density of electrons on the ionosphere between the sattelite and the reception antenna. The TEC goes through regular variances, which behaviour can be verified during the day, throughout seasons and also throughout cycles of approximately eleven years (related to the ocorrence of sunspot). Besides these variances, extreme solar events such as solar flares and coronal mass ejection may cause abrupt and significant changes to TEC behavior, exerting big influence in GPS positioning, mainly to monofrequency receptors. In Brazil, the ionosphere factor is even more relevant because this region is affected by phenomena such as the Equatorial Anomaly (EA), the South Atlantic Magnetic Anomaly (SAMA) and even by the ocorrence of ionospheric irregularities. In order to develop knowledge about the relation between ionosphere and GPS positioning in Brazil, on this research TEC and GPS data were analised in periods of high and low solar activity, as well as in a geomagnetic perturbed period. The results showed direct relation between the decreasing of TEC, in the low solar activity period, and the improving of GPS positioning. This improving has resulted in a reduction of 59% in the planimetric error and 64% in the altimetric error in the point positioning and a reduction of 65% in the planimetric error and 63% in the altimetric error in the relative positioning. During the period affected by a severe geomagnetic storm, a completely atypical behavior was identified in the ionosphere, making the results of the relative positioning much worse in unexpected times and locations.

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9

Brückner, Marlen, Michael Lonardi, André Ehrlich, et al. "Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC)." Leibniz-Institut für Troposphärenforschung, 2020. https://ul.qucosa.de/id/qucosa%3A74381.

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The thermosphere-ionosphere regions are mainly controlled by the solar, but also by geomagnetic activity. In this case study, the Earth’s ionospheric response to the 25-26 August 2018 intense geomagnetic storm is investigated using the International GNSS System (IGS) Total Electron Content (TEC) observations. During this major storm, the minimum disturbance storm time (Dst) index reached -174 nT. We use observations and model simulations to analyse the ionospheric response during the initial phase and the main phase of the magnetic storm. A significant difference between storm day and quiet day TEC is observed. The O/N2 ratio observed from the GUVI instrument onboard the TIMED satellite is used to analyse the storm effect. The result shows a clear depletion of the O/N2 ratio in the high latitude region, and an enhancement in the low latitude region during the main phase of the storm. Furthermore, the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model simulations were used. The results suggest that the CTIPe model can capture the ionospheric variations during storms. Die Regionen der Ionosphären und Thermosphäre werden hauptsächlich von der Sonne sowie auch von geomagnetische Aktivität beeinflusst. In dieser Fallstudie wurde die ionosphärische Reaktion der Erde auf den starken geomagnetischen Sturm vom 25./26. August 2018 unter Verwendung der Gesamtelektronengehaltsdaten (Total Electron Content, TEC) vom Internationalen GNSS Service untersucht. Während dieses großen Sturms wurde ein ”Disturbance Storm Time Index” Dst von -174 nT erreicht. Beobachtungen und Modellsimulationen wurden verwendet, um die ionosphärische Reaktion während der Anfangsphase und der Hauptphase des magnetischen Sturms zu untersuchen. Ein signifikanter Unterschied zwischen TEC während eines Sturmtages und eines ruhigen Tages wurde beobachtet. Das vom GUVI-Instrument an Bord des TIMED-Satelliten beobachtete O/N2 -Verhältnis wurde verwendet, um den Sturmeffekt weiter zu untersuchen. Das Ergebnis zeigt eine deutliche Abnahme/Zunahme des O/N2 Verhältnis in hohen/niedrigen Breiten während der Hauptphase des Sturms. Darüber hinaus wurde das Coupled Thermosphere Ionosphere Plasmasphere ectrodynamics (CTIPe) Modell verwendet. Die Ergebnisse legen nahe, dass das CTIPe-Modell die ionosphärischen Schwankungen während eines Sturms erfassen kann.

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Matsuoka, Marcelo Tomio [UNESP]. "Influência de diferentes condições da ionosfera no posicionamento por ponto com GPS: avaliação na região brasileira." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/100257.

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Made available in DSpace on 2014-06-11T19:30:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-28Bitstream added on 2014-06-13T21:01:19Z : No. of bitstreams: 1 matsuoka_mt_dr_prud.pdf: 13818049 bytes, checksum: ffbf4629b778855c81e385452f044bfb (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Após a desativação da técnica SA, a ionosfera tornou-se a principal fonte de erro no posicionamento com GPS. O erro associado à ionosfera é diretamente proporcional ao conteúdo total de elétrons (TEC - Total Electron Content) presente ao longo do caminho da trajetória percorrida pelo sinal na ionosfera e inversamente proporcional ao quadrado da freqüência do sinal. O TEC, e conseqüentemente o erro devido à ionosfera, variam no tempo e no espaço e é influenciado por diversas variáveis, tais como: ciclo solar, época do ano, hora do dia, localização geográfica, atividade geomagnética, entre outros. A região brasileira é um dos locais que apresenta os maiores valores e variações espaciais do TEC e onde estão presentes diversas particularidades da ionosfera, tais como, a anomalia equatorial e o efeito da cintilação ionosférica. Desta forma, é importante a realização de pesquisas que visam estudar o comportamento do TEC, e conseqüentemente do erro devido à ionosfera no Brasil, que é um trabalho complexo devido aos diversos fatores que influenciam a variação do TEC, além das particularidades presentes na região brasileira. Estudos desta natureza podem auxiliar a comunidade geodésica brasileira, e demais usuários do GPS, no entendimento das limitações impostas pela ionosfera nas regiões de interesse. Devido à natureza dispersiva da ionosfera, o estudo do comportamento do TEC no Brasil pode ser realizado utilizando os dados GPS de receptores de dupla freqüência pertencentes à RBMC (Rede Brasileira de Monitoramento Contínuo). Adicionalmente, para uma melhor análise, pode-se também utilizar dados das estações da rede IGS (International GNSS Service) da América do Sul. In the SA absence, the ionosphere is the largest error source in GPS positioning. The error due to the ionosphere in the GPS observables depends on the signal frequency and Total Electron Content (TEC) in the ionospheric layer. The TEC varies regularly in time and space in relation to the sunspot number, the season, the local time, the geographic position, and others. The Brazilian region is one of the regions of the Earth that presents largest values and space variations of the TEC, being influenced by the equatorial anomaly of ionization and ionospheric scintillation. Therefore, it is important to study the TEC behavior in the Brazilian region. Due to the ionosphere dispersive nature, the TEC behavior in Brazil can be studied using GPS data from RBMC (Rede Brasileira de Monitoramento Contínuo - Brazilian Network for Continuous Monitoring of GPS). Additionally, GPS data from IGS (International GNSS Service) network of the South America can also be used in the experiments.

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Booth, Timothy Charles. "Magnetospheric response to geomagnetic storms." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42328.

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Geomagnetic storms are well observed phenomena that enhance the plasma of the inner magnetosphere to high energies. They are defined by the characteristic trace in indices that measure the variation of the north-south component of the Earth’s magnetic field, such as the Dst or SYM-H. These indices are not purely measures of the symmetric ring current but include components of other current systems within the magnetosphere, primarily the tail and magnetopause currents. Using the methodology of Asikainen et al. [2010] the SMR index has been deconstructed to observe the evolution of the aforementioned current systems over the storm durations. Reeves et al. [2003] showed that only half of all storms caused an increase in the relativistic electron flux at geosynchronous orbit. For the remaining half the electron flux either does not change or decreases. It has been shown that the ring current decays faster for flux decrease storms than flux increase storms. Using a superposed epoch analysis, of geomagnetic indices and solar wind parameters, it has also been shown that although flux increase storms tend to have faster, less dense solar wind in the recovery phase of storms, it appears that it is the orientation of the IMF, which remains more southward in the recovery phase, that is the key parameter. This allows for the continued injection of plasma sheet particles into the inner magnetosphere. Further evidence to support this has been shown with the hydrogen and helium fluxes mirroring that of the electron flux. Finally, potential wave modes were evaluated over storm durations and potential acceleration mechanisms were noted as being more intense during flux increase storms than flux decrease storms; this is most likely due to the increase in the seed particles necessary for their generation.

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Suresh, Padmashri. "Global Thermospheric Response to Geomagnetic Storms." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5001.

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Geomagnetic storms deposit energy and momentum into the Earth’s magnetosphere which in turn energizes the terrestrial atmosphere through Joule heating and particle precipitation. This storm energy predominantly converges at altitudes of 100 to 150 km, corresponding to the lower thermospheric region, which is then globally redistributed throughout the thermosphere. It is essential that we understand the times and magnitudes of this energy to understand the terrestrial atmospheric response to geomagnetic storms. However, our current knowledge is mostly limited to the studies of orbital altitudes of the thermosphere. We aim to fill this gap by conducting a statistical study of lower thermospheric response to geomagnetic storms. We use neutral temperature data from SABER (Sounding of the Atmosphere Using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere, Ionosphere, and Mesosphere Energy Dynamics) satellite for this study. We devise a procedure to extract the storm response from SABER temperature measurements and deduce the magnitudes and times of the global storm energy redistribution in the 100 to 120 km altitude of the thermosphere. We use methods of inferential and descriptive statistics to investigate the lower thermospheric response for 145 storm intervals that occurred between 2002 and 2010. We also investigate the performance of the state-ofart physics and empirical models in replicating the lower thermosphere during geomagnetic storms.

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Sidhu, Rajbir. "Impacts of geomagnetic storms on trans-Canadian grids." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97253.

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Impacts of Geomagnetic storms on Trans-Canadian GridsInduced "dc" currents due to geomagnetic storms have caused power system blackouts and transformer damages in the past. Statistically, large geomagnetic storms follow a 10-11 year sunspot cycle, but geomagnetic disturbances with significant impacts can occur at any time. The geomagnetically induced currents (GIC) have wide range of detrimental effects on otherwise normal operation of power systems, communication systems, railway systems, and can cause oil and gas pipeline corrosion. This thesis presents a method of estimating the magnitudes of terrestrial voltages; which is based on solving the magnetic diffusion equation. The method predicts the oft-quoted figure of "1 volt per kilometer" for the range of geomagnetic field variations (magnitudes and frequencies) and ground resistivity frequently encountered. The prediction formula has been validated by the plane wave method. Geomagnetic storms have the tendency to disrupt the normal operation and even lead to major power outages depending upon the intensity of geomagnetic activity; whereas the major effects include transformer equipment damage, relay tripping, SVC failures resulting in minor or major power outages. RÉSUMÉImpacts of Geomagnetic storms on Trans-Canadian GridsPar le passé, les courants induits produits par des orages électromagnétiques ont causés des dommages à des transformateurs ainsi que des pannes de courant majeures (blackouts). Statistiquement, les orages géomagnétiques sévères suivent un cycle d'activité solaire de 10 à 11 ans. Cependant, des perturbations géomagnétiques peuvent avoir un impact important et peuvent apparaître à n'importe quel moment. Les courants induits géomagnétiques ont un large champ d'effets néfastes sur les réseaux électriques, les systèmes de communication, les systèmes ferroviaires et peuvent causer de la corrosion dans les oléoducs. Cette thèse présente une méthode pour estimer l'amplitude des tensions terrestres qui est basée sur les équations de diffusion magnétique. Cette méthode prédit la figure couramment utilisée de « 1 volt par kilomètre » pour une étendue de champs géomagnétiques (amplitudes et fréquences) et de résistances du sol fréquemment rencontrées. La formule de prédiction a été validée par la méthode d'onde plane.Les orages géomagnétiques ont tendance à déranger les opérations normales et même à engendrer des pannes électriques majeures dépendamment de l'intensité de l'activité géomagnétique. Les principaux effets sont des dommages à l'équipement des transformateurs, des déclenchements de relais de protection, des défaillances des compensateurs statiques (SVC), ce qui causent parfois des pannes de courant mineures ou majeures.

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14

Yin, Ping. "Ionization dynamics under the influence of geomagnetic storms." Thesis, University of Bath, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436768.

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The Earth ionosphere becomes highly variable during extreme space-weather events. Observations from the Global Positioning System (GPS) in conjunction with tomographic imaging have the potential to characterise its disturbed behaviour. In this project, a four-dimensional tomographic technique is employed to reveal the temporal evolution and spatial distribution of ionisation in the ionosphere on a large scale (over Europe and the USA). The effects of geomagnetic storms on the dynamics of the plasma are investigated throughout the recent solar maximum, when the intensity of geornagnetic storms is greatest. The results presented in this thesis show, for the first time, a wide area view of the ionosphere during storm-time. Electron-density images of the disturbed mid/high latitude ionosphere and Total Electron Content (TEC) maps are produced over North America and Europe for several severe storms. Using both ground-based and Low Earth Orbit satellite-based GPS data as well as available ionosonde data during storm periods, improvements in imaging of ionospheric structures at storm time are made. A case-study for the 29th - 30th October 2003 storm shows the detailed evolution of ionisation in space and in time throughout the entire period of a complex storm. The peak heights of the disturbed F region were redistributed (uplifted) both over Europe and the USA around dusk for several major storm events. This uplift propagated westwards. Investigations into common features of storms indicated that positive or negative storm effects correlated with local time. In addition, the strongest enhancement in TEC and the highest uplift were in the USA sector. The project achievements are twofold. Firstly, abnormal behaviour of the disturbed ionosphere,such as enhancements in electron density and TEC and sudden uplifts of the peak height, is shown using a new GPS imaging technique. Secondly, the results will provide important experimental inputs into physical models of ionospheric storms and also contribute to the further understanding the dynamics of ionisation and underlying mechanisms of severe storms on a global scale.

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15

Pressling, Nicola Justine. "Pacific geomagnetic secular variation : the story from Hawaii." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441187.

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16

Wolfe, Elizabeth Ann. "Understanding thermospheric neutral density response during geomagnetic storms." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460882.

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17

Uwamahoro, Jean. "An analysis of sources and predictability of geomagnetic storms." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1005236.

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Solar transient eruptions are the main cause of interplanetary-magnetospheric disturbances leading to the phenomena known as geomagnetic storms. Eruptive solar events such as coronal mass ejections (CMEs) are currently considered the main cause of geomagnetic storms (GMS). GMS are strong perturbations of the Earth’s magnetic field that can affect space-borne and ground-based technological systems. The solar-terrestrial impact on modern technological systems is commonly known as Space Weather. Part of the research study described in this thesis was to investigate and establish a relationship between GMS (periods with Dst ≤ −50 nT) and their associated solar and interplanetary (IP) properties during solar cycle (SC) 23. Solar and IP geoeffective properties associated with or without CMEs were investigated and used to qualitatively characterise both intense and moderate storms. The results of this analysis specifically provide an estimate of the main sources of GMS during an average 11-year solar activity period. This study indicates that during SC 23, the majority of intense GMS (83%) were associated with CMEs, while the non-associated CME storms were dominant among moderate storms. GMS phenomena are the result of a complex and non-linear chaotic system involving the Sun, the IP medium, the magnetosphere and ionosphere, which make the prediction of these phenomena challenging. This thesis also explored the predictability of both the occurrence and strength of GMS. Due to their nonlinear driving mechanisms, the prediction of GMS was attempted by the use of neural network (NN) techniques, known for their non-linear modelling capabilities. To predict the occurrence of storms, a combination of solar and IP parameters were used as inputs in the NN model that proved to predict the occurrence of GMS with a probability of 87%. Using the solar wind (SW) and IP magnetic field (IMF) parameters, a separate NN-based model was developed to predict the storm-time strength as measured by the global Dst and ap geomagnetic indices, as well as by the locally measured K-index. The performance of the models was tested on data sets which were not part of the NN training process. The results obtained indicate that NN models provide a reliable alternative method for empirically predicting the occurrence and strength of GMS on the basis of solar and IP parameters. The demonstrated ability to predict the geoeffectiveness of solar and IP transient events is a key step in the goal towards improving space weather modelling and prediction.

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18

Phiri, Temwani-Joshua. "Correlation between SQUID and fluxgate magnetometer data for geomagnetic storms." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80364.

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Thesis (MScEng)--Stellenbosch University, 2013. ENGLISH ABSTRACT: Geomagnetic storms are primarily driven by the rapid transfer of energy from the solar wind to the magnetosphere. The mechanism of energy transfer involves the merging of the interplanetary magnetic field to the geomagnetic field in a process known as magnetic reconnection. This leads to an influx of energetic, charged particles into the magnetosphere so that current systems are enhanced. Specifically, an increase in the equatorial ring current leads to a decrease in the surface field. Geomagnetic storms are thus characterized by a strong decline in the horizontal components of the geomagnetic field, lasting from several hours to days. The intensity of a storm is described by the disturbed storm-time index, which is essentially a measure of the deviation from the typical quiet day variation along the equator. Severe storms can lead to the disruption of high frequency (HF) communications as a consequence of a strongly perturbed ionosphere. By the same token, the global positioning system (GPS) can become highly unreliable during magnetically disturbed conditions, yielding distance errors as large as 50 meters. The impact of geomagnetic activity and other solar-driven processes on technology systems are collectively known as space weather. Magnetic field sensing thus forms an important part of space weather forecasting and is vital to space science research as a means of improving our understanding of solar wind-magnetosphere interactions. This study examines the use of magnetometers built as SQUIDs (Superconducting Quantum Interference Devices) for monitoring the geomagnetic field for space weather forecasting purposes. A basic theory of superconductivity is presented and subsequently the key aspects governing the operation of SQUIDs are discussed. Space weather is also introduced with respect to the various processes on the sun that perturb the magnetosphere and hence the geomagnetic field. The method of analysis was basically to Fourier-transform the data using the Wiener-Khintchine theorem. A systematic approach to Fourier analysis is thus presented, demonstrating the superiority of the Wiener-Khintchine theorem in noise reduction. The suitability of SQUID magnetometers for space science research is demonstrated by a comparative study between SQUID and fluxgate datasets for magnetic storms during 2011. Strong correlation was observed between the frequency content of the SQUID and fluxgate signals. This result supports South Africa’s SQUID project, currently undertaken as a collaborative effort between SANSA Space Science and the Department of Electrical and Electronic Engineering at Stellenbosch University. This thesis thus lays a foundation for future research involving advanced magnetometry using SQUIDs. AFRIKAANSE OPSOMMING: Geomagnetiese storms word hoofsaaklik gedryf deur die vinnige oordrag van energie van die sonwind na die magnetosfeer. Die meganisme van energie oordrag behels die samesmelting van die interplanetêre magneetveld met die geomagneetveld, in 'n proses wat bekend staan as magnetiese heraansluiting. Dit lei tot 'n instroming van energieke elektries-gelaaide deeltjies, tot in die magnetosfeer, met die gevolg dat magnetosferiese elektriese stroomstelsels versterk word. 'n Toename in die ekwatoriale ringstrome lei spesifiek tot 'n afname in die horisontale komponent van die geomagnetiese veld. Geomagnetiese storms word dus gekenmerk deur 'n sterk afname in die horisontale komponent van die geomagnetiese veld, ‘n afname wat etlike ure tot dae kan duur. Die intensiteit van 'n storm word beskryf deur die storm-tyd versteurings indeks , 'n maatstaf van die afwyking van die tipiese stil dag magnetiese variasie langs die ewenaar. Ernstige storms kan lei tot die ontwrigting van hoë frekwensie (HF) kommunikasie as 'n gevolg van 'n erg versteurde ionosfeer. Soortgelyk kan die Globale Posisionering Stelsel (GPS) hoogs onbetroubaar word tydens magneties versteurde toestande, en posisiefoute so groot as 50 meter veroorsaak. Die impak van geomagnetiese aktiwiteit en ander sonkrag gedrewe prosesse op tegnologie is gesamentlik bekend as ruimteweer. Magneetveldmetinge vorm dus 'n belangrike deel van ruimteweervoorspelling en is noodsaaklik vir ruimtewetenskaplike navorsing as 'n middel om die sonwind-magnetosfeer interaksies beter te verstaan. Hierdie studie ondersoek die gebruik van SQUID (Engels: Superconducting Quantum Interference Device) magnetometers vir die monitering van die geomagnetiese veld vir ruimteweervoorspellingsdoeleindes. ’n Basiese teorie van supergeleiding word aangebied, waarvolgens die sleutelaspekte van SQUIDs bespreek word. Ruimteweer word ook voorgestel in terme van die verskillende prosesse op die son wat die aarde se magnetosfeer en dus die geomagnetiese veld versteur. Die analisemetode wat hier gebruik word, is om die Fourier-transform van data met die Wiener-Khintchine theorema te bereken. A sistematiese metode vir Fourier-analise word aangebied, wat die superiorireit van die Wiener-Khintchine teorema vir ruisvermindering demonstreer. Die geskiktheid van SQUID magnetometers vir ruimtewetenskaplike navorsing word gedemonstreer deur ’n vergelykende studie tussen SQUID- en vloedhek-datastelle vir magnetiese storms gedurende 2011. Sterk korrelasie is waargeneem tussen die frekwensie-inhoud van die SQUID- en vloedhekseine. Hierdie resultate ondersteun Suid-Afrika se SQUID-projek, wat tans as ’n samewerkingspoging tussen SANSA Space Science en die Departement Elektriese en Elektroniese Ingenieurswese aan die Universiteit van Stellenbosch bedryf word. Hierdie tesis lê ’n fondasie vir toekomstige navorsing oor gevorderde magnetometrie met SQUIDs.

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Ngwira, Chigomezyo Mudala. "An analysis of ionospheric response to geomagnetic disturbances over South Africa and Antarctica." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1012957.

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The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.

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Hutchinson, James A. "Geomagnetic storms over the last solar cycle : a superposed epoch analysis." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/29033.

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This thesis investigates energy transfer between solar wind (SW)-magnetosphere-ionosphere systems during geomagnetic storms that could pose a significant threat to terrestrial technology. A superposed epoch analysis (SEA) of 143 storms from the last solar cycle (1997-2008) was completed. The average geomagnetic storm was investigated via SW data and the global SYM-H index. A new dual trend was observed when comparing storm size to main phase duration which reduced for storms with SYM-H minima <-150 nT, opposite to the findings of Yokoyama and Kamide [1997]. This suggests ring current enhancement dominates recovery, meaning intense storms can occur on the same timescales as weak; important for space weather prediction. One of the first global SEA studies of storm time ionospheric convection using HF SuperDARN radars and map potential technique was completed. Latitude-Time-Velocity plots were developed to best observe the average convection response to storm driving compared to quiet periods and Gillies et al. [2011]. A case study was presented comparing the SEA results to two recent storms, showing remarkable agreement, suggesting the SEA average convection could be used in future predictions. An SEA of global UV auroral images from the IMAGE and Polar spacecraft produced expected auroral responses to geomagnetic storm driving (e.g. Milan et al. [2009]). Open-closed field line boundaries, identified using the method of Boakes et al. [2008], were compared to convection reversal boundaries derived from the SuperDARN analysis. Consistent statistical boundary o_sets suggested a small 'viscous-like' interaction between the SW and magnetosphere was present, estimated to produce an additional ∽4-11 kV potential during quiet and storm periods; an important, small addition to the usual reconnection driven convection. These studies increase our understanding of storm time SW-magnetosphere-ionosphere coupling, raising interesting questions for future work. The combination of datasets makes this one of the largest statistical studies of storms.

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Matladi, Thabang-Kingsley. "Correlation between SQUID and Fluxgate Magnetometer Data-sets for Geomagnetic Storms: Hermanus." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86627.

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Thesis (MEng)--Stellenbosch University, 2014. ENGLISH ABSTRACT: Superconducting QUantum Interference Devices (SQUIDs) are fairly recent types of magnetometers that use flux quantization combined with Josephson tunnelling to detect very faint (< 10¯15 T) magnetic fields. Recent scientific studies have shown that these highly sensitive magnetometers, located in an ultra-low-noise environment, are capable of observing Earth-ionosphere couplings, such as P waves emitted during earthquakes or magnetic storms in the upper atmosphere, S and T breathing modes of the Earth during quiet magnetic and seismic periods, signals in time correlating with sprites. Since SQUIDs are much more sensitive than conventional magnetometers, they are arguably the best tool for understanding space weather and natural hazards, whether they are produced from space or within the ionosphere by magnetic storms for instance, or natural disturbances, including magnetic disturbances produced by earthquakes or as a result of the dynamics of the earth's core. A study was conducted at SANSA Space Science in Hermanus, Western Cape, in 2012, to find the correlation between SQUID and Fluxgate data-sets, with the aim of validating the use of a SQUID as a reliable instrument for Space Weather observations. In that study, SQUID data obtained from the Low Noise Laboratory (LSBB) in France was compared to Fluxgate data-sets from the three closest magnetic observatories to LSBB, namely Chambon la For êt (France), Ebro (Spain) and Fürstenfeldbruck (Germany), all further than 500 km from LSBB. As a follow-up study, our aim is to correlate the SANSA Space Science SQUID data at Hermanus with Fluxgate magnetic data also recorded on-site (at Hermanus). There are notable di_erences between the previous study and the current study. In the previous study, the three-axis SQUID used comprised of three low-Tc devices operated in liquid helium (4.2 K) in an underground, low noise environment shielded from most human interferences. The SQUID magnetometer operated at Hermanus for the duration of this study is a high-Tc two-axis device (measuring the x and z components of the geomagnetic field). This SQUID magnetometer operates in liquid nitrogen (77 K), and is completely unshielded in the local geomagnetic field of about 26 uT. The environment is magnetically clean to observatory standards, but experiences more human interference than that at LSBB. The high-Tc SQUIDs also experience excessive 1/f noise at low frequencies which the low-Tc SQUIDs do not suffer from, but the big advantage of the current study is that the SQUIDs are located within 50 m from the observatory's fluxgate. We thus expect far better correlation between SQUID and fluxgate data than what was obtained in the previous study, which should improve the isolation of signals detected by the SQUID but not by the fluxgate. AFRIKAANSE OPSOMMING: SQUIDs (supergeleidende kwantuminterferensietoestelle) is redelik onlangse tipes magnetometers wat vloedkwantisering saam met Josephson-tonneling gebruik om baie klein (< 10¯15 T) magnetiese velde waar te neem. Onlangse wetenskaplike studies het getoon dat hierdie hoogs sensitiewe magnetometers die vermoë het om Aarde-ionosfeerkoppeling waar te neem wanneer dit in 'n ultra-laeruisomgewing geplaas word. Sodanige koppeling sluit in: P-golwe wat deur aardbewings or magnetiese storms in die boonste atmosfeer veroorsaak word; S- en T-asemhalingsmodusse van die Aarde gedurende stil magnetiese en seismiese periodes; en seine in tyd wat korreleer met weerligeffekte in die boonste atmosfeer. Aangesien SQUIDs heelwat meer sensistief is as konvensionele magnetometers, is dit moontlik die beste gereedskap om ruimteweer en geassosieerde natuurlike gevare mee te analiseer; hetsy sulke toestande veroorsaak word vanaf die ruimte (deur die son) of binne die ionosfeer deur magnetiese storms of natuurlike steurings wat deur aardbewings of die dinamika van die Aardkern veroorsaak word. 'n Studie is in 2012 gedoen by SANSA Space Science in Hermanus in die Wes-Kaap om die korrelasie tussen SQUID- en vloedhekdatastelle te vind met die doel om SQUIDs as betroubare instrumente vir ruimteweerwaarneming te bevestig. In daardie studie is SQUID-data verkry vanaf die Laeruis Ondergrondse Laboratorium (LSBB) in Frankryk, en is dit vergelyk met vloedhekdatastelle vanaf die drie naaste magnetiese observatoriums aan LSBB, naamlik: Chambon la Forêt (Frankryk), Ebro (Spanje) en Fürstenfeldbruck (Duitsland). Al drie hierdie observatoriums is verder as 500 km vanaf LSBB. As 'n opvolgstudie is ons doelwit om SQUID- en vloedhekdata wat beide op die terrein van SANSA Space Science in Hermanus waargeneem word, te korreleer. Daar is merkbare verskille tussen hierdie en die vorige studies. In die vorige studie is 'n drie-as lae-Tc SQUID-magnetometer in vloeibare helium (4.2 K) in 'n laeruis ondergrondse laboratorium, afgeskerm teen menslike steurings, gebruik. Die SQUID-magnetometer wat vir die duur van die huidige studie by Hermanus gebruik is, is 'n hoë-Tc twee-as toestel (wat die x - en z -komponente van die geomagnetiese veld meet). Hierdie SQUID-magnetometer opereer in vloeibare stikstof teen 77 K, sonder enige afskerming in die geomagnetiese veld van ongeveer 26 uT. Die omgewing is magneties skoon volgens observatoriumstandaarde, maar ondervind meer menslik-veroorsaakde steurings as LSBB. Die hoë-Tc SQUIDs tel ook heelwat 1/f ruis op (wat lae-frekwensiemetings beïnvloed); iets wat nie 'n rol speel by die lae-Tc SQUIDs nie. Die groot voordeel van die huidige studie is dat die SQUIDs binne 50 meter vanaf die observatorium vloedhekke geleë is. Ons verwag dus heelwat beter korrelasie tussen SQUID- en vloedhekdata as wat met die vorige studie verkry is, wat dit makliker sal maak om die isolasie te verbeter van seine wat deur die SQUIDs waargeneem is, maar nie deur die vloedhekke nie.

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Patra, Swadesh. "The Contribution of Magnetospheric Currents to Ground Magnetic Perturbation during Geomagnetic Storms." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1719.

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A geomagnetic storm is triggered in response to a disturbance in the solar wind. The earth's ring current gets energized during a geomagnetic storm, which leads to a decrease in the horizontal component of the geomagnetic field on the earth's surface. The Disturbance Storm Time (Dst) index, which is a measure of the intensity of the ring current, is calculated by taking the average of this decrease in the horizontal intensity across four low latitude magnetometer stations and removing the quiet time secular variations. The rate of decrease of the Dst index is an indicator of the deenergization of the ring current particles. But there are several issues with the Dst measurement as a proxy of the ring current energy. In particular, the percentage contribution of the tail current effect to the Dst index is still debated. In this work, an effort has been made to separate and quantify the possible contribution of the tail current to the Dst index. The relative contribution for a selected set of storms for which the interplanetary magnetic field turned northward abruptly after the peak in Dst was observed is estimated. The WINDMI model of the nightside magnetosphere is used to investigate the contributions of ring current, magnetotail current, and magnetopause current on the observed two-phase decay of the Dst index. The role of different solar wind magnetosphere coupling functions on the Dst index calculated by the WINDMI model is also investigated. The performance of four other coupling functions in addition to the rectified vBs is evaluated. These coupling functions emphasize different physical mechanisms to explain the energy transfer into the magnetosphere due to solar wind velocity, dynamic pressure, magnetic field, and Mach number. One coupling function is due to Siscoe, another by Borovsky, and two by Newell. The results indicate that for a majority of cases, at most only vx, By, and Bz are needed to sufficiently account for the supply of energy to the ring current and geotail current components that contribute to the Dst index. The capabilities of the WINDMI model to reliably determine the state of the global magnetosphere are improved by employing the the Magnetotail (MT) index as a measurement constraint during large geomagnetic storms. The MT index is used as a proxy for the strength of the magnetotail current in the magnetosphere. The inclusion of the MT index as an optimization constraint in turn increases our confidence that the ring current contribution to the Dst index calculated by the WINDMI model is correct during large geomagnetic storms. To improve the models prediction of AL index, we also modify the ionospheric conductivity and fit to two substorms. The rate of reduction of convection in the magnetotail for some of these storms is numerically simulated by using inner magnetospheric models like the Fok Ring Current (FRC) and the Rice Convection Model along with the global BATSRUS model at the community coordinated modeling center. Model results are compared against magnetometer data by creating movie maps from several low-latitude magnetometer stations. The results indicate the contribution from the tail current to the Dst is important. In addition, the reduction of the cross-tail current during substorm dipolarization is predicted by the measured isotropic boundary locations. Several well known phenomena are identified in the magnetometer movie maps.

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Matamba, Tshimangadzo Merline. "Long-term analysis of ionospheric response during geomagnetic storms in mid, low and equatorial latitudes." Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/63991.

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Understanding changes in the ionosphere is important for High Frequency (HF) communications and navigation systems. Ionospheric storms are the disturbances in the Earth’s upper atmosphere due to solar activities such as Coronal Mass Ejections (CMEs), Corotating interaction Regions (CIRs) and solar flares. This thesis reports for the first time on an investigation of ionospheric response to great geomagnetic storms (Disturbance storm time, Dst ≤ −350 nT) that occurred during solar cycle 23. The storm periods analysed were 29 March - 02 April 2001, 27 - 31 October 2003, 18 - 23 November 2003 and 06 - 11 November 2004. Global Navigation Satellite System (GNSS), Total Electron Content (TEC) and ionosonde critical frequency of F2 layer (foF2) data over northern hemisphere (European sector) and southern hemisphere (African sector) mid-latitudes were used to study the ionospheric responses within 15E° - 40°E longitude and ±31°- ±46° geomagnetic latitude. Mid-latitude regions within the same longitude sector in both hemispheres were selected in order to assess the contribution of the low latitude changes especially the expansion of Equatorial Ionization Anomaly (EIA) also known as the dayside ionospheric super-fountain effect during these storms. In all storm periods, both negative and positive ionospheric responses were observed in both hemispheres. Negative ionospheric responses were mainly due to changes in neutral composition, while the expansion of the EIA led to pronounced positive ionospheric storm effect at mid-latitudes for some storm periods. In other cases (e.g 29 October 2003), Prompt Penetration Electric Fields (PPEF), EIA expansion and large scale Traveling Ionospheric Disturbances (TIDs) were found to be present during the positive storm effect at mid-latitudes in both hemispheres. An increase in TEC on the 28 October 2003 was because of the large solar flare with previously determined intensity of X45± 5. A further report on statistical analysis of ionospheric storm effects due to Corotating Interaction Region (CIR)- and Coronal Mass Ejection (CME)-driven storms was performed. The storm periods analyzed occurred during the period 2001 - 2015 which covers part of solar cycles 23 and 24. Dst≤ -30 nT and Kp≥ 3 indices were used to identify the storm periods considered. Ionospheric TEC derived from IGS stations that lie within 30°E - 40°E geographic longitude in mid, low and equatorial latitude over the African sector were used. The statistical analysis of ionospheric storm effects were compared over mid, low and equatorial latitudes in the African sector for the first time. Positive ionospheric storm effects were more prevalent during CME-driven and CIR-driven over all stations considered in this study. Negative ionospheric storm effects occurred only during CME-driven storms over mid-latitude stations and were more prevalent in summer. The other interesting finding is that for the stations considered over mid-, low, and equatorial latitudes, negative-positive ionospheric responses were only observed over low and equatorial latitudes. A significant number of cases where the electron density changes remained within the background variability during storm conditions were observed over the low latitude stations compared to other latitude regions.

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Olukayode, Falayi Elijah. "Statistical Analysis of Geomagnetic Storms Global Effects and Space Weather Influence on Energy and Fuel Industry." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506921.

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Cích, Augustín. "Nízkoúrovňového měření ELF magnetických polí." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442410.

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This Master's thesis deals with design of sensor network for synchronised low-level recording of changes in magnetic part of Earth's field in ELF band in multiple places. The goal is acquisition of changes due to solar storm activity, while taking into account, that in research of geomagnetic effects connected with solar events is spectrum of interest broader and reach up to VLF, where a solution is often made of combination of receivers in ELF and VLF, a decision was made, after consulting with thesis supervisor and researchers, that device will be designed for ELF, but can be easily modified, by changing preamplifier, for using in higher frequency bands, creating a solid founding for further measurements and research in this field.

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Compagnino, Antonio Alessio. "Properties and correlation of flares and coronal mass ejections and their possible relevance on the southern night sky background: a statistical study." Doctoral thesis, Università di Catania, 2018. http://hdl.handle.net/10761/3814.

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This Thesis is devoted to a statistical study of solar phenomena (flares and coronal mass ejections) and their possible effects on the Earth. The Sun, our star, can be considered a huge laboratory where we can study the interaction of a ionized gas with magnetic fields. In particular, the solar atmosphere (the outer layers of the Sun, those which are accessible to observations) is characterized by phenomena that due their existence to localized magnetic fields: sunspots, faculae, filaments, active regions, bright points, coronal holes, etc. The occurrence of these phenomena is variable, depending on the so-called activity cycle, characterized by a period of 11 years. Moreover, in some situations, the magnetic field that permeates the active regions, from an initial potential field configuration (characterized by the minimum energy content), can slowly store energy, changing its configuration to more complex and more energetic ones. When the magnetic field configuration is not able to maintain its equilibrium, the stored magnetic energy is abruptly released, giving rise to phenomena that are generally termed as solar eruptions but that, depending on their characteristics, are distinguished between flares, filament eruptions and coronal mass ejections. In the last decades, the possibilities offered by new computer capabilities, new instruments and by satellite observations, have allowed us to understand many of the characteristics of these eruptions, as well as their effects on the Earth magnetosphere and ionosphere. However, despite the progress in our comprehension of these phenomena, there are still many aspects that need to be clarified: how and where is the energy stored, what causes the trigger of the eruption, how the different phenomena are related to each other and how they can affect our environment, to cite only a few. In this scenario, the work carried out in this Thesis has been motivated by three main questions: -- Are there preferential locations on the Sun where the magnetic field is prone to produce eruptive events ? -- What kind of correlation exists between flares (mainly confined to the solar atmosphere) and coronal mass ejections that, by definition, expel magnetized clouds into the interplanetary space ? -- Can the charged particles emitted during these events and arriving to the Earth ionosphere have a role in the observed variations of the night-sky background? The attempt to provide answers to the previous questions has been faced in this Thesis from an observational / statistical point of view. More precisely, the dataset that have been used in order to answer the first two questions have been retrieved from public archives of flares and coronal mass ejections relevant to the last two solar cycles (23 and 24), while in order to provide an answer to the third question, also data acquired by the Pierre Auger Observatory have been used. The main results obtained in this Thesis can be summarized as follows: -- The spatial and temporal distribution of the flares analyzed show persistent domains of occurrence within well defined belts of longitude, with a behavior similar to the one observed for other activity phenomena, like the sunspots. -- There is a temporal correlation between flares and CMEs for the 60 % of the events analyzed; the time interval (between 10-130 minutes) however depends on the dataset used. Moreover, the majority of CMEs with highest velocities show a clear temporal correlation with flares. -- The variations in the night-sky background analyzed for the nights when a major impact of charged particles associated to CMEs was expected, could not be clearly correlated to these events.

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Anaya, José Carlos Tacza. "Análise do campo elétrico atmosférico durante tempo bom e distúrbios geofísicos." Universidade Presbiteriana Mackenzie, 2015. http://tede.mackenzie.br/jspui/handle/tede/1302.

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Made available in DSpace on 2016-03-15T19:35:52Z (GMT). No. of bitstreams: 1 JOSE CARLOS TACZA ANAYA.pdf: 7682166 bytes, checksum: f3eebed2cf5cb0f5ecda9415f8754978 (MD5) Previous issue date: 2015-01-19 Conselho Nacional de Desenvolvimento Científico e Tecnológico In this dissertation, we present the capability of a new network of sensors to monitor the atmospheric electric field at various locations in South America. The main goal is to obtain the characteristic Universal Time daily curve of the atmospheric electric field in fair-weather. That curve is known as the Carnegie curve, which is related to the currents flowing in the Global Atmospheric Electric Circuit. This has been accomplished using monthly, seasonal and annual averages. After obtaining our standard curve of variation of the electric field in fair-weather, the deviations related to phenomena such as solar flares, solar protons events, geomagnetic storms, total solar eclipse and seismic activity are analyzed and commented. Neste trabalho de dissertação apresenta-se a capabilidade de uma nova rede de sensores para monitorar o campo elétrico atmosférico em vários locais na América do Sul. O objetivo principal é obter a curva diária do campo elétrico atmosférico de tempo bom. Para isto foram realizadas médias mensais, sazonais e anuais. Essa curva é comparada com a curva característica em Tempo Universal conhecida como a Curva de Carnegie, a qual é relacionada com as correntes fluindo no Circuito Elétrico Atmosférico Global. Depois de obter a curva padrão de variação do campo elétrico atmosférico de tempo bom, foram analisados e comentados os desvios relacionados a explosões solares, eventos de prótons solares, tempestades geomagnéticas, eclipse solar e atividade sísmica.

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Yamamoto, Kazuhiro. "Excitation of High-m Poloidal ULF Waves in the Inner Magnetosphere during Geomagnetic Storms and Substorms: Importance of Radial Gradient of Proton Distributions in Drift-Bounce Resonance." Kyoto University, 2020. http://hdl.handle.net/2433/253099.

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Martineau, Ryan J. "Parameterized Least-Squares Attitude History Estimation and Magnetic Field Observations of the Auroral Spatial Structures Probe." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4482.

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Terrestrial auroras are visible-light events caused by charged particles trapped by the Earth's magnetic eld precipitating into the atmosphere along magnetic eld lines near the poles. Auroral events are very dynamic, changing rapidly in time and across large spatial scales. Better knowledge of the low of energy during an aurora will improve understanding of the heating processes in the atmosphere during geomagnetic and solar storms. The Auroral Spatial Structures Probe is a sounding rocket campaign to observe the middle-atmosphere plasma and electromagnetic environment during an auroral event with multipoint simultaneous measurements for fine temporal and spatial resolution. The auroral event in question occurred on January 28, 2015, with liftoff the rocket at 10:41:01 UTC. The goal of this thesis is to produce clear observations of the magnetic eld that may be used to model the current systems of the auroral event. To achieve this, the attitude of ASSP's 7 independent payloads must be estimated, and a new attitude determination method is attempted. The new solution uses nonlinear least-squares parameter estimation with a rigid-body dynamics simulation to determine attitude with an estimated accuracy of a few degrees. Observed magnetic eld perturbations found using the new attitude solution are presented, where structures of the perturbations are consistent with previous observations and electromagnetic theory.

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Kutschenko, Andressa. "Associação entre tempestades geomagnéticas e internações por infarto agudo do miocárdio." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/17/17139/tde-18012013-094335/.

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Os diversos fenômenos solares mostram que a sua atividade não é constante, sendo as manchas solares observadas em sua fotosfera um indicador de atividade do Sol. Os números dessas manchas seguem um ciclo de 11 anos que alterna entre máximos e mínimos; quanto maior o número de manchas, maior o número de erupções no Sol. A literatura médica vem mostrando algumas evidências de que a atividade solar possui alguma relação com a predisposição das pessoas a algumas doenças. As tempestades geomagnéticas são associadas a doenças cardiovasculares, mudanças na pressão arterial sistólica, gravidade da crise de enxaqueca, distúrbios psiquiátricos. As condições da atividade geomagnética são classificadas segundo Batista (2003) em uma escala de Calma, Transição, Ativo, Tempestade fraca, Tempestade intensa ou Tempestade muito intensa. No presente projeto de pesquisa, objetiva-se investigar a associação entre atividade geomagnética e internações diárias por infarto nos hospitais de Ribeirão Preto e região, no período de 1998 a 2007. A hipótese em estudo é que em dias de condições de atividade geomagnética muito perturbada, o número médio de internações por doenças isquêmicas do coração é maior. Para a análise dos dados foi utilizado o modelo de regressão de Poisson com função logarítmica com o auxílio do software SAS 9.2, utilizando o procedimento PROC GENMOD. Observa-se que há evidências de associação entre tempestades geomagnéticas e internações por IAM. Numerous solar phenomena demonstrate that their activities are not continual, and sunspots noticed in their photosphere are considered an indicator by Suns activity. Numbers linked with these sunspots follow an eleven-year cycle, which alternates between high and low, it means, the greater the number of sunspots, the greater the number of Sun eruptions. Medical Literature has produced evidences that solar activity has some association with people predisposing to some diseases. Geomagnetic storms are related with cardiovascular disease, changes in systolic blood pressure, severity and psychiatric disorders. According to Batista (2003), geomagnetic activity conditions are categorized on a scale of Quiet, Transition, Acting, Weak Storm, Intense Storm or Very Intense Storm. This study intends to investigate the association between geomagnetic activity and daily hospitalization by acute myocardial infarction (AMI) in Ribeirão Preto and its region from 1998 to 2007. The hypothesis being studied is that: day which has unquiet geomagnetic condition, the average number of hospitalizations originated by ischemic heart disease is higher. In order to get on with data analysis, it was used Poissons regression model, with logarithmic function through SAS 9.2, using PROC GENMOD procedure. In consequence, it is observed that there are evidences between geomagnetic storms and hospitalizations by AMI.

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Segarra, Blasco Antoni. "Detecció automàtica de començaments abruptes de tempestes magnètiques utilitzant xarxes neuronals." Doctoral thesis, Universitat Ramon Llull, 2014. http://hdl.handle.net/10803/283880.

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L’objectiu d’aquesta tesi és la detecció automàtica de començaments abruptes de tempestes magnètiques (Sudden Commencements, SC). Per assolir aquest objectiu primerament hem situat el fenomen d’estudi, els SCs, dintre el marc general del geomagnetisme. Els SCs són un fenomen que es caracteritza per un augment sobtat del camp geomagnètic. Presenta unes característiques clares com són un temps d’inici ben definit, la simultaneïtat a tot el planeta i una font ben establerta com és l’augment abrupte de la pressió del vent solar. Però també presenta una morfologia complexa depenent on està situat l’observatori en qüestió, les diferències morfològiques depenen de la latitud i l’hora local dels observatoris. Hem fet un esforç per entendre la història de l’estudi dels SCs, per veure les seves dificultats i l'evolució tant de la nomenclatura com de la seva definició. Actualment la morfologia dels SCs està ben explicada a través del model físic d’Araki [Araki, 1994]. Hem estudiat a fons un cas particular, des de l’increment de la pressió del vent solar fins als registres dels observatoris terrestres. Així, hem pogut veure les diferències entre l’aspecte dels SCs observats per diferents satèl•lits i a terra, on presenta una morfologia molt més complexa per l’acció dels corrents ionosfèrics i els corrents existents a la magnetosfera. Amb aquest cas particular hem vist la complexitat del fenomen i també hem mostrat la validesa del model teòric. Pel que fa a la detecció dels SCs hem explicat l’estat actual del procés d’elaboració de les llistes d’esdeveniments i les seves dificultats que fan necessari la cerca d’un mètode de detecció automàtic. Per abordar aquest repte hem optat per treballar en xarxes neuronals per la seva capacitat d’aprendre a partir de casos. A efecte de valorar la idoneïtat de les xarxes neuronals per resoldre problemes en el camp del geomagnetisme, les hem aplicat per un problema concret: obtenir índexs d’activitat magnètica locals a partir d’índexs globals. Obtenint, per aquest cas, resultats satisfactoris especialment en situacions d’activitat magnètica moderada o alta. Com a resultat fonamental d’aquesta tesi, presentem un mètode basat en les xarxes neuronals capaç de detectar els SCs de forma automàtica, ràpida, sistemàtica i essent coherent amb el mètode manual. Aquest nou mètode pot treballar tant amb dades de molts observatoris, però també amb pocs observatoris treballa satisfactòriament. Si treballem amb els observatoris de baixa latitud, on la forma dels SCs normalment s’assembla més a una funció esglaó, podem assegurar que la llista produïda amb la xarxa és totalment coherent amb les llistes tradicionals. El objetivo de esta tesis es la detección automática de comienzos abruptos de tormentas magnéticas (Sudden Commencements, SC). Para alcanzar este objetivo, en primer lugar, hemos situado el fenómeno de estudio, los SCs, dentro del marco general del geomagnetismo. Los SCs son un fenómeno que se caracteriza por un aumento repentino del campo geomagnético. Presenta unas características claras como son un tiempo de inicio bien definido, simultaneidad en todo el planeta y una fuente bien conocida como es el aumento abrupto de la presión del viento solar. Pero también presenta una morfología compleja dependiendo de donde está situado el observatorio en cuestión, las diferencias morfológicas dependen de la latitud y la hora local de los observatorios. Hemos hecho un esfuerzo para entender la historia del estudio de los SCs, para ver sus dificultades y la evolución tanto de su nomenclatura como de su definición. Actualmente, la morfología de los SCs está bien explicada a través del modelo físico de Araki [Araki, 1994]. Hemos estudiado a fondo un caso particular, desde el incremento de la presión del viento solar hasta los registros de los observatorios terrestres. Así, hemos podido ver las diferencias entre el aspecto de los SCs observados por diferentes satélites y en tierra, donde presenta una morfología mucho más compleja por la acción de las corrientes ionosféricas y las corrientes existentes en la magnetosfera. Con este caso particular hemos visto la complejidad del fenómeno y también hemos mostrado la validez del modelo teórico. Respecto a la detección de los SCs, hemos explicado el estado actual del proceso de elaboración de las listas de sucesos y sus dificultades que hacen necesario la búsqueda de un método automático. Para abordar este reto hemos optado por trabajar con redes neuronales por su capacidad de aprender a partir de casos. A efectos de valorar la idoneidad de las redes neuronales para resolver problemas en el campo del geomagnetismo, las hemos aplicado para un problema concreto: obtener índices de actividad magnética locales a partir de índices globales. Obteniendo, para este caso, resultados satisfactorios especialmente en situaciones de actividad magnética moderada o alta. Como resultado fundamental de esta tesis, presentamos un método basado en redes neuronales capaz de detectar los SCs de forma automática, rápida, sistemática y siendo coherente con el método manual. Este nuevo método puede trabajar con datos de muchos observatorios, pero también con pocos observatorios trabaja satisfactoriamente. Si trabajamos con los observatorios de baja latitud, donde la forma de los SCs normalmente se parece más a una función escalón, podemos asegurar que la lista producida con la red neuronal es totalmente coherente con las listas tradicionales. The aim of this thesis is the automatic detection of sudden commencements of magnetic storms (SC). To achieve this goal we first located the phenomenon of study, SC, within the general framework of geomagnetism. The SC is a phenomenon characterized by a sudden increase of the geomagnetic field. Its characteristics are a clear and well-defined onset time, simultaneity across the globe and a well-established source such as the sudden increase of solar wind pressure. But it also presents a complex morphology depending on where the specific observatory is located; the morphological differences depend on the local time and latitude of the observatories. We have made an effort to understand the history of the study of SCs to see their difficulties and therefore the evolution of the nomenclature and its definition. Currently, the morphology of the SCs is well explained through the physical model of Araki [Araki, 1994]. We have studied deeply a particular case, from the increase pressure of the solar wind to the observations on the Earth. Thus, we could see the differences between the appearance of SCs observed by various satellites and on the Earth, where SC presents a much more complex morphology by the action of ionospheric currents and currents existing in the magnetosphere. In this particular case we have seen the complexity of the phenomenon and have shown the validity of the theoretical model. Regarding the detection of SCs we have explained the current state of the process of drawing up lists of events and its difficulties that make necessary to search for an automatic detection method. To deal with this challenge we have chosen to work with neural networks for its ability to learn from cases. For the purposes of assessing the suitability of neural networks to solve problems in the field of geomagnetism, we have applied to a specific problem: get local magnetic activity indices from global indices. We have obtained for this case satisfactory result, especially in cases of moderate or high magnetic activity. As a fundamental result of this thesis, we present a method based on neural networks able to detect SCs automatically, quickly, systematically and consistent with the manual method. This new method can both work with data from many observatories, but also works successfully with few observatories. If we work with low-latitude observatories, where the shape of the SCs usually is more like a step function, we can ensure that the list produced by the network is fully consistent with the traditional lists.

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Jen, Ts'ai Ying, and 蔡穎仁. "Characteristics of Geomagnetic Pulsation Before and After Magnetic Storm at Chung-Li Area." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/13556652300502870226.

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碩士 國立中央大學 太空科學研究所 83 Pc型地磁微脈動可分為Pc1 、Pc2 、Pc3 、Pc4 、Pc5 ，用FFT的技巧，可以將地磁微脈動的頻譜分析出來，再用極化分析的方法研究這些頻帶的極化主軸偏向與極化方向。今由觀測資料得知：磁暴發生後，微脈動周期有變長(Pc4 - Pc5)及變短(Pc2) 的現象，而寧靜時期的微脈動大致上為 Pc3 。在理論方面，根據 HASEGAWA 及 CHEN 的理論，再配合實際觀測資料（午前、午後的極化主軸大都在二、四象限）得知：上午電離層的電子密度往下漸增，而下午電離層的電子密度往下漸減。中壢地區屬於地磁特低緯地區，地磁微脈動會受電離層之影響，並且不同於中、高緯地區微脈動之特性，有其研究價值。 Continuous magnetic pulsations are classified as Pc1,Pc2, Pc3, Pc4, and Pc5. We use fast Fourier transform (FFT) to get the spectra of geomagnetic micropulations. By the method of polarization analysis, we obtain the orientation of major axis and the sense of polarization. From the data analysis, it is found that the pulsations of Pc4 - Pc5 and Pc2 after the occurrence of geomagnetic storm are observed. Pulsations are within the Pc3 band during quiet time. The observed major axis lies in the second-fourth quadrants in both the morning side and the evening side. Based on the theory of Hasegawa and Chen, the density gradient of the electrons in ionosphere is positive and negative toward the ground in the morning and in the evening, respectively. The area of Chung-Li is at geomagnetic very low latitude, therefore, the pulsations are influenced by the ionosphere. The characteristics of pulsation of this area are different from that of middle and high geomagnetic latitudes.

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Kouba, Daniel. "Ionosférická driftová měření." Doctoral thesis, 2014. http://www.nusl.cz/ntk/nusl-334575.

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Title: Ionospheric drift measurements Author: Daniel Kouba Department: Department of Surface and Plasma Science Supervisor: RNDr. Petra Koucká Knížová, Ph.D. Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic Abstract: This thesis deals with ionospheric drift measurements using Digisonde DPS-4. The results are divided into theoretical and practical part. It is shown that for drift data processing it is necessary to choose correct reflection points corresponding to drift movements first. The selection is made in three steps: restriction of Doppler frequency shift, height range selection, choice of the maximum zenith angle. After- wards it is possible to credibly estimate the vector of drift velocity. The experimental results of drift measurements are based on data from the Pru- honice station. To study the common behavior of ionospheric drifts during quiet conditions, the statistical characteristics of drift velocity components are investiga- ted in layers E and F during geomagnetic quiet year 2006. The maximal daily amplitude of horizontal velocity demonstrates the influence of geomagnetic activity. It is proved to be considerable in the F layer meanwhile it was not observed in the E layer. The effect of strong geomagnetic disturbances is shown at two examples of extreme storms. The...

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Mays, Mona Leila. "The study of interplanetary shocks, geomagnetic storms, and substorms with the WINDMI model." 2009. http://hdl.handle.net/2152/10703.

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WINDMI is a low dimensional plasma physics-based model of the coupled magnetosphere-ionosphere system. The nonlinear system of ordinary differential equations describes the energy balance between the basic nightside components of the system using the solar wind driving voltage as input. Of the eight dynamical variables determined by the model, the region 1 field aligned current and ring current energy is compared to the westward auroral electrojet AL index and equatorial geomagnetic disturbance storm time Dst index. The WINDMI model is used to analyze the magnetosphere-ionosphere system during major geomagnetic storms and substorms which are community campaign events. Numerical experiments using the WINDMI model are also used to assess the question of how much interplanetary shock events contribute to the geoeffectiveness of solar wind drivers. For two major geomagnetic storm intervals, it is found that the magnetic field compressional jump is important to producing the changes in the AL index. Further, the WINDMI model is implemented to compute model AL and Dst predictions every ten minutes using real-time solar wind data from the ACE satellite as input. Real-Time WINDMI has been capturing substorm and storm activity, as characterized by the AL and Dst indices, reliably since February 2006 and is validated by comparison with ground-based measurements of the indices. Model results are compared for three different candidate input solar wind driving voltage formulas. Modeling of the Dst index is further developed to include the additional physical processes of tail current increases and sudden commencement. A new model, based on WINDMI, is developed using the dayside magnetopause and magnetosphere current systems to model the magnetopause boundary motion and the dayside region 1 field aligned current which is comparable to the auroral upper AU index. text

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Shah, Asif. "The interaction of storm-time ULF waves with Earth’s radiation belts in the presence of a realistic ionosphere boundary." Thesis, 2017. http://hdl.handle.net/1959.13/1354289.

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Research Doctorate - Doctor of Philosophy (PhD) The outer Van Allen radiation belt becomes unstable during geomagnetic storms, when the fluxes and energies of geomagnetically trapped particles fluctuate by several orders of magnitude. Ultra-low frequency (ULF) plasma waves are widely believed to play an important role in accelerating radiation belt particles to ‘killer’ energies that may damage space assets and contribute to other space weather hazards. Previous work on the role of these wave-particle interactions has usually focused either on in-situ observations or simulation studies. Most of the previous simulation studies have ignored the ionosphere boundary, or treated it as a perfectly conducting boundary in the ideal limit or as an electrostatic layer by ignoring the Hall conductivity. Although the polar ionosphere boundaries were included in the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model, the effect of ionospheric Pedersen and Hall conductances on wave-particle interactions was not studied. This thesis for the first time includes the effects of realistic ionosphere boundaries into test-particle simulations of ULF wave-particle interactions in Earth’s magnetosphere. The ionosphere boundary is characterized by finite and nonzero values of the height integrated direct, Hall, and Pedersen conductances. Four distinct studies are included in the thesis, each forming a manuscript to be submitted for publication or published in the peer reviewed literature. The first study shows that four types of ionosphere boundaries (ideal reflector, daytime with no Hall conductivity, realistic night-time, and realistic daytime) each result in unique distributions of kinetic energy and radial diffusion coefficients for equatorially mirroring electrons. It is also shown that the electron trajectory and kinetic energy for a perfectly conducting ionosphere temporally evolve in distinctly different ways from the temporal behaviours of electron trajectories and kinetic energies due to ULF waves modelled in the presence of realistic ionosphere boundaries. This study for the first time shows that treatments of ULF wave-particle interactions in the magnetosphere cannot ignore the effects of realistic ionosphere boundary conditions. The second study examines storm time in-situ observations of ULF waves and electron fluxes on 7 January 2011. A magnetohydrodynamic (MHD) model incorporating realistic ionosphere boundaries is used to simulate ULF wave propagation in the magnetosphere at this time. In these simulations the wave toroidal and poloidal electric fields are comparable to those measured by the THEMIS satellites during the event. Test-particle simulations of wave-electron interactions in the equatorial plane show flux enhancements which agree with observations from the THEMIS-A satellite. It is also shown that the temporal rate of electron energization increases with decreasing ionosphere conductance. The significance of the ionosphere conductance, the ULF wave frequency, and particle trapping due to field line resonances (FLRs) are examined. The third study examines storm time in-situ observations of ULF waves and proton flux enhancements on 8 October 2013. The MHD model of ULF wave propagation is used with realistic dusk side values of the Hall and Pedersen conductances. The simulations produce wave electric fields comparable with those measured by the electric field and wave (EFW) instruments on the Radiation Belt Storm Probes (RBSP) satellites, and the electric field instrument (EFI) on the THEMIS-E satellite. Test-particle simulations are used to examine the evolution of wave-particle interactions at various locations off the equator. Proton flux observations are explained via these simulations. It is also shown that increasing ionospheric Hall and Pedersen conductances decrease the amplitudes of the wave electric fields, which in turn reduces proton energization. The fourth study shows that when the north and south ionosphere boundaries are symmetric then the amplitudes of the toroidal and poloidal electric fields in the northern and southern hemispheres are also equal. However, for asymmetric ionosphere boundaries high amplitude ULF electric fields occur in the hemisphere with small values of ionosphere conductances. The effects of symmetric and asymmetric ionospheres are compared with the energization of bouncing and drifting protons via test-particle simulations of ULF wave-proton interactions.

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Schillings, Audrey. "O+ outflow during geomagnetic storms observed by Cluster satellites." Licentiate thesis, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68586.

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The region of space dominated by the Sun's magnetic field is called the heliosphere. It envelops the entire solar system including Earth. Therefore, a strong coupling exists between the Sun and our planet. The Sun continuously ejects particles, the solar wind, and when these high energy particles hit Earth, the magnetosphere (the region around the Earth governed by the geomagnetic field) is affected. When the solar wind is enhanced this disturbs the magnetosphere and perturbations can be seen also in ground-based observations. The upper atmosphere is subjected to solar radiation that ionise the neutral atoms and molecules, this region is referred to as the ionosphere. In the ionosphere, some of the heavier ion populations, such as O+, are heated and accelerated through several processes and flow upward. In the polar regions these mechanisms are particularly efficient and when the ions have enough energy to escape the Earth's gravity, they move outward along open magnetic field lines and may be lost into interplanetary space. Ion outflow in general has already been well studied, however, ion outflow under extreme magnetospheric conditions has not been investigated in detail. Disturbed magnetospheric conditions correlate with solar active periods, such as coronal holes or the development of solar active regions. From these regions, strong ejections called coronal mass ejections (CMEs) emerge. When these extreme events interact with Earth, they produce a compression of the magnetosphere as well as reconnection between the terrestrial magnetic field lines and the interplanetary magnetic field (IMF) lines, which most of the time leads to geomagnetic storms. The amounts of incoming solar particles and energy increase during geomagnetic storms and we also observe an increase in the O+ outflow. Our observations are made with the Cluster mission, a constellation of 4 satellites flying around Earth in the key magnetospheric regions where ion outflow is usually observed. In this thesis, we estimate O+ outflow under disturbed magnetospheric conditions and for several extreme geomagnetic storms. We find that O+ outflow lost into the solar wind increases exponentially with enhanced geomagnetic activity (Kp index) and increases about 2 orders of magnitude during extreme geomagnetic storms. Den del av rymden som domineras av solens magnetfält kallas heliosfären. Helios-fären omfattar hela solsystemet inklusive jorden, vilket gör att det finns en starkkoppling mellan solen och jorden. Solen sänder oavbrutet ut laddade partiklar in denså kallade solvinden och när dessa energika partiklar träffar jorden påverkas mag-netosfären (det område kring jorden där det geomagnetiska fältet dominerar). Närsolvinden är starkare än vanligt uppstår störningar. I magnetosfären som ger effektersom kan uppmätas med markbaserade instrument. Den övre atmosfären utsätts för strålning från solen som joniserar atomer ochmolekyler, och formar det område som kallas jonosfären. Några av de tyngre jonpop-ulationerna i jonosfären, som till exempel syrejoner, kan hettas upp och accelererasgenom flera olika möjliga processer. Detta gör att de flödar uppåt i atmosfären. Ipolarområdena är dessa mekanismer särskilt effektiva och om tillräckligt med energitillförs jonerna kan gravitationen övervinnas, vilket gör att jonerna flödar upp längsöppna magnetfältlinjer och kan gå förlorade ut i den interplanetära rymden. Generelltsett har jonutflöde redan studerats väl, men jonutflöde under extrema magnetosfäriskaförhållanden har inte undersökts i detalj. Störda magnetosfäriska förhållanden korrelerar med då solen är aktiv, som tillexempel koronahål eller under utvecklingen av aktiva solområden. Från dessa områ-den härstammar koronamassautkastningar. När dessa extrema händelser når jordenkomprimeras magnetosfären och det geomagnetiska och interplanetära magnetiskafältet omkopplas, vilket ofta leder till geomagnetiska stormar. Under dessa införsstora mängder av partiklar i solvinden och energi till magnetosfären, och ett högresyrejonsutflöde är också observerat. Data från Clustersatelliterna har använts; dessa utgörs av fyra satelliter i for-mation i omloppsbana kring jorden. Plasmaområdena där de befinner sig är därjonutflödet vanligtvis observeras. Denna avhandling behandlar syrejonsutflöde understörda magnetosfäriska förhållanden och flera extrema geomagnetiska stormar. Detvisas att syrejonsutflödet som förloras till solvinden ökar exponentiellt med geomag-netiskt aktivitet (Kp-index) och ökar med upp till 2 storleksordningar under extremageomagnetiska stormar.

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Song, Hui. "Automatic prediction of solar flares and super geomagnetic storms." Thesis, 2008. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2008-046.

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Spencer, Edmund Augustus. "Analysis of geomagnetic storms and substorms with the WINDMI model." Thesis, 2006. http://hdl.handle.net/2152/2604.

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Yu, Bin. "Simulation of dynamics of radiation belt electrons during geomagnetic storms driven by high speed solar wind streams." Thesis, 2007. http://hdl.handle.net/1911/20672.

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Satellite observations have shown that fluxes of relativistic electrons in the earth's radiation belts can vary by orders of magnitude during periods of high solar activity. Understanding the dynamic behavior of these particles is very important because they can disrupt wireless communication, impair space exploration and affect GPS navigation. We use two numerical methods to simulate the variations of energetic particles in the radiation belts. First, we develop a radial diffusion model with time-dependent boundary conditions and a Kp-dependent electron lifetime model. Using this model, we simulate a series of high-speed-stream declining-phase magnetic storm events. The results are consistent with spacecraft observations and show that radial diffusion can propagate the enhancement of phase space density from the outer boundary into the center of the outer radiation belt. The second part of the work adapts Nunn's Vlasov Hybrid Simulation method to an existing MHD-Particle simulation code, resulting in an efficient new method to calculate phase space density of energetic particles. We use the 1995 January storm event as a test case. Good agreement is obtained between the simulation results and measured phase space densities for this event. Simulating the dynamics of the radiation belts is one important part of global space weather modeling. The advance in radiation belt modeling can help us to better understand the physics behind these interesting and important phenomena.

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Francisco, Cristiana Filipa Pereira. "Preliminary study of the sensitivity to geomagnetic storms of the power network substations in Portugal south region." Master's thesis, 2020. http://hdl.handle.net/10316/92484.

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Dissertação de Mestrado em Astrofísica e Instrumentação para o Espaço apresentada à Faculdade de Ciências e Tecnologia A rede elétrica portuguesa é suscetível a tempestades geomagnéticas, que criam correntes geomagnéticas induzidas (GICs) que afetam os transformadores das subestações da rede. Este trabalho começa com uma revisão do processo de acoplamento Sol-Terra, com foco no vento solar como elemento de conexão. Em seguida, é feita uma aplicação original do código de Pethick para explicar o efeito dos modelos de condutividade 1D no cálculo da matriz de impedância MT, seguida por uma análise original de cinco tempestades geomagnéticas durante o início da fase de declínio do ciclo solar 24, combinando dados geomagnéticos do observatório magnético de Coimbra com dados de satélite dos parâmetros do vento solare. Em seguida é usada uma combinação de um determinado modelo simplificado de condutividade, para a região sul de Portugal continental, com os sinais de tempestade geomagnética para produzir gráficos originais do campo elétrico induzido, destacando o efeito da costa. Isso leva, finalmente, ao uso original de uma versão modificada do código GEOMAGICA, num modelo da região sul de Portugal, para testar a sensibilidade de diferentes subestações a uma mudança nas tempestades geomagnéticas e nos parâmetros de resistência de aterramento. Este trabalho também conclui que algumas subestações dificilmente sentem alguma diferença quando a resistência de aterramento é alterada, mas outras sentem, e o facto de se considerar o valor standard de 0.20 Ohm pode resultar num erro de cálculo da GIC da ordem de sim 10%. The Portuguese power network is susceptible to geomagnetic storms, which create geomagnetic induced currents (GICs) that affect the transformers of the network substations. This work starts with a review on the Sun-Earth coupling process focusing on the solar wind as the connecting element. Then it is made an original application of Pethick to explain the effect of 1D conductivity models on the computation of the MT impedance matrix followed by an original analysis of five geomagnetic storms during the begin of decline phase of solar cycle 24, combining geomagnetic data of the magnetic observatory of Coimbra with satellite data of solar wind parameters. Next it is used a combination of a given simplified model of conductivity for the southern region of Portugal mainland with the geomagnetic storm signals, to produce original charts of the induced electric field, highlighting the coast effect. This leads to, finally, an original use of a modified version of the GEOMAGICA code on a model of the Portuguese southern region, to test the sensitivity of different substations to a change in the geomagnetic storms and in the earthing resistance parameters. It is found that the STVR substation has the highest GIC maximum for each storm and that the stronger the geomagnetic storm, the more intense is the GIC in the substations. This work also conclude that some substations hardly feel some difference when the earthing resistance is changed but others do, and the assumption of 0.20 Ohms values can result in a GIC miscalculation of the order of 10%.

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Lee, Eun Ah. "Large Scale ULF Waves and Energetic Particles in the Earth's Magnetosphere." Phd thesis, 2011. http://hdl.handle.net/10048/1729.

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In this thesis we examine the generation mechanisms of Pc 5 ULF waves during geomagnetic storms. Also, we study the interaction between Pc 5 ULF waves and energetic particles in the radiation belts and the observed energetic particle flux modulation by Pc 5 ULF waves is verified using particle simulations. Firstly, we present case studies of Pc 5 pulsations using ground-based magnetometer and satellite data during geomagnetic storm times, specifically we selecting three storm time events which show a brief increase in Dst in the main phase of the storms. By studying these events, we attempt to identify the generation mechanisms responsible for the geomagnetic pulsations. The observed pulsations exhibit the characteristic features of a Field Line Resonance. Our results also show evidence for the penetration of ULF wave power in the Pc 5 band to much lower L-shells than normal, suggesting significant reduction of the local Alfven eigenfrequency continuum as compared to non-storm times. This may have considerable significance for the interaction between ULF waves and MeV electrons in the outer radiation belt during storms. Secondly, based on the hypothesis that Pc 5 ULF waves may play an important role in energetic particle dynamics in the radiation belt and ring current, we investigated the relationship between Pc 5 pulsations and energetic particle flux oscillations. We observed very strong Pc 5 oscillations during the great magnetic storm of March 24, 1991 [Lee et al., 2007] and electron flux simultaneously oscillating with the same frequencies in the time domain. We also characterize two more events and present an examination of the relationship between the electron flux modulation and Pc 5 ULF pulsations. Based on our observations, the modulation of energetic particles might be associated with a drift-resonance interaction, or the advection of an energetic particle density gradient. Finally, we numerically calculate the trajectories and energy change of charged particles under the influence of model ULF wave electric fields. This modeling work is used to help to explain the observations and provides evidence which supports the modulation mechanisms such as advection of a flux gradient and drift resonance.

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"Space Weather Event Modeling of Plasma Injection Into the Inner Magnetosphere with the Rice Convection Model." Thesis, 2011. http://hdl.handle.net/1911/70447.

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The inner magnetosphere modeling is an important component of the magnetosphere simulation frameworks with significant implications for space weather and a. principle methodology to understand the magnetospheric response to changes in the solar wind. The thesis shows our efforts in constructing and validating the contemporary Rice Convection Model (RCM) code and its interface as a next-generation code to predict electric fields, field-aligned currents, and energetic particle fluxes in the inner magnetosphere and subauroral ionosphere during geomagnetic disturbed times. The RCM was used to simulate the geomagnetic storms with fixed boundary conditions of time-dependent Tsyganenko-Mukai boundary conditions. This work shows the results of two extremely- strong storm events with significant interchange motion. The ring current injection predicted by the RCM is shown to be overestimated, consistent with the previous results of overestimating particle fluxes by the RCM. This effect is magnified here since the southward component of interplanetary magnetic field is very strong reaching about 50 nT. Time-dependent Borovsky's boundary condition is implemented and used to alleviate the huge pressure and get better tendency of ring current energy calculated by the Dessler-Parker-Sckopke relation. This work also describes a new module of generalized Knight's relation to compute the parallel potential drops from the calculated field-aligned currents through Vasyliunas equation. It gives different ionospheric conductance and plasma drift signatures particularly around the midnight. The inclusion of parallel electric fields will replace the treatments of energy flux in the substorm simulations since that the Hardy normalization cannot perform the desired function during the substorm expansion phase and the energy flux floor gives arbitrary enhanced the precipitating energy flux and ionospheric conductances at high latitude especially for the westward clectrojet around the midnight. Since the original Knight's relation gives too large field-aligned potential drop, the modified Knight's relation is applied and implemented successfully into the RCM. Therefore, the RCM is capable of real time event simulation including strong geomagnetic storms and magnetospheric substorms, although full validation of model predictions with typical observations remains to be done.

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Dissertations / Theses on the topic 'Geomagnetic storm'

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