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Articoli di riviste sul tema "Ionosphere – Africa – Radio waves"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 7 febbraio 2022

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1

Roger, Nakolemda, Nanema Emmanuel e Sawadogo Gedeon. "MODELING CRITICAL FREQUENCY OF IONOSPHERE D-LAYER AT MINIMUM AND MAXIMUM OF THE SOLAR CYCLE 22WITH IRI-2016". International Journal of Advanced Research 9, n. 08 (31 agosto 2021): 960–65. http://dx.doi.org/10.21474/ijar01/13349.

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One of the interests of the study of the ionosphere lies in its importance for the transmission of radio waves in telecommunications. The ionospherebehaves as an obstacle to the passage of waves. Thus, the signals of short wavelengths are reflected by the F layer or the upper part of the sublayer E, while theD-layeris the seat of the reflection of low-frequencywaves. The presentstudyinvestigates the temporal variability of the criticalfrequency of the D-layer (for) using the 2016 version of the International Reference Ionosphere (IRI) model under quiet day conditions during at maximum and minimum phase of solar cycle 22. The workisconductedat the Ouagadougou station, located in West Africa. The methodology of the workadopted for the determination of the parameter foDisbased on the calculation of the monthlyhourlyaverages of this variable obtainedwith the help of the model during the monthsthatcharacterize the seasons. The resultsobtained for the parameter for as a function of time during the minimum and maximum of the solar cycle 22 have been presented. The seasonal and temporal variations of the criticalfrequency of the ionosphereD-layer show that the foD values are lower during a minimum of the solar cycle and present maximum values at the Zenith (1200 TL) at a minimum and maximum. Theseresultsalsorevealthatthisparameter varies with time, season, and geographical position. The results of thisstudy show a criticalfrequencybelow 1 MHz during both phases of the solar cycle.

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2

Barta, Veronika, Gabriella Sátori, Kitti Alexandra Berényi, Árpád Kis e Earle Williams. "Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa". Annales Geophysicae 37, n. 4 (23 agosto 2019): 747–61. http://dx.doi.org/10.5194/angeo-37-747-2019.

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Abstract. We have investigated the solar flare effects on ionospheric absorption with the systematic analysis of ionograms measured at midlatitude and low-latitude ionosonde stations under different solar zenith angles. The lowest recorded ionosonde echo, the minimum frequency (fmin, a qualitative proxy for the “nondeviative” radio wave absorption occurring in the D-layer), and the dfmin parameter (difference between the value of the fmin and the mean fmin for reference days) have been considered. Data were provided by meridionally distributed ionosonde stations in Europe and South Africa during eight X- and M-class solar flares in solar cycle 23. Total and partial radio fade-out was experienced at every ionospheric station during intense solar flares (> M6). The duration of the total radio fade-out varied between 15 and 150 min and it was highly dependent on the solar zenith angle of the ionospheric stations. Furthermore, a solar-zenith-angle-dependent enhancement of the fmin (2–9 MHz) and dfmin (1–8 MHz) parameters was observed at almost every station. The fmin and dfmin parameters show an increasing trend with the enhancement of the X-ray flux. Based on our results, the dfmin parameter is a good qualitative measure for the relative variation of the “nondeviative” absorption, especially in the case of the less intense solar flares, which do not cause total radio fade-out in the ionosphere (class < M6).

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3

Altadill, David, Antoni Segarra, Estefania Blanch, José Miguel Juan, Vadym V. Paznukhov, Dalia Buresova, Ivan Galkin, Bodo W. Reinisch e Anna Belehaki. "A method for real-time identification and tracking of traveling ionospheric disturbances using ionosonde data: first results". Journal of Space Weather and Space Climate 10 (2020): 2. http://dx.doi.org/10.1051/swsc/2019042.

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Traveling Ionospheric Disturbances (TIDs) are wave-like propagating irregularities that alter the electron density environment and play an important role spreading radio signals propagating through the ionosphere. A method combining spectral analysis and cross-correlation is applied to time series of ionospheric characteristics (i.e., MUF(3000)F2 or foF2) using data of the networks of ionosondes in Europe and South Africa to estimate the period, amplitude, velocity and direction of propagation of TIDs. The method is verified using synthetic data and is validated through comparison of TID detection results made with independent observational techniques. The method provides near real time capability of detection and tracking of Large-Scale TIDs (LSTIDs), usually associated with auroral activity.

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4

Waters, C. L., T. K. Yeoman, M. D. Sciffer, P. Ponomarenko e D. M. Wright. "Modulation of radio frequency signals by ULF waves". Annales Geophysicae 25, n. 5 (4 giugno 2007): 1113–24. http://dx.doi.org/10.5194/angeo-25-1113-2007.

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Abstract. The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1–100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B0, giving an e×B0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF) Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.

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5

Nanema, Emmanuel, Moustapha Konate, Doua Allain Gnabahou e Frederic Ouattara. "Effects of Height of F2-Layer on Critical Frequency by Use of Data at Ouagadougou Station". Applied Physics Research 10, n. 5 (27 settembre 2018): 57. http://dx.doi.org/10.5539/apr.v10n5p57.

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Ionosphere investigation leads to the knowledge of its composition in particles. The particle density and composition determine the capacity of this region to reflect radio waves in the atmosphere at different heights. Some variables such as season, solar cycle phase also influence the ionosphere behavior. Radio waves frequencies pass through the ionosphere layer without reflection above a critical value determining the critical frequency. This study determines the critical frequency of radio waves in the F2 layer (foF2) of the ionosphere by use of data at Ouagadougou station during the minimum and the maximum of solar cycle 22, at different seasons with the height of F2-layer (hmF2). Daytime and nighttime also influence ionosphere parameters. The study presents the hourly behavior of foF2 according to hmF2 values.

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6

Naumov, N. D. "Passage of short radio waves through the lower ionosphere". Plasma Physics Reports 38, n. 13 (dicembre 2012): 1007–11. http://dx.doi.org/10.1134/s1063780x12060086.

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7

Nina, A., e V. M. Čadež. "Detection of acoustic‐gravity waves in lower ionosphere by VLF radio waves". Geophysical Research Letters 40, n. 18 (16 settembre 2013): 4803–7. http://dx.doi.org/10.1002/grl.50931.

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8

Lebedev, N. V., N. D. Naumov e V. V. Rudenko. "Simulation of lower ionosphere heating by modulated radio-frequency waves". Plasma Physics Reports 39, n. 13 (dicembre 2013): 1068–73. http://dx.doi.org/10.1134/s1063780x13070155.

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9

Nielsen, E., D. D. Morgan, D. L. Kirchner, J. Plaut e G. Picardi. "Absorption and reflection of radio waves in the Martian ionosphere". Planetary and Space Science 55, n. 7-8 (maggio 2007): 864–70. http://dx.doi.org/10.1016/j.pss.2006.10.005.

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10

Zawdie, K. A., D. P. Drob, D. E. Siskind e C. Coker. "Calculating the absorption of HF radio waves in the ionosphere". Radio Science 52, n. 6 (giugno 2017): 767–83. http://dx.doi.org/10.1002/2017rs006256.

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11

Plotkin, V. V., e N. I. Izraileva. "Resonance scattering of radio waves in the acoustically disturbed ionosphere". Radiophysics and Quantum Electronics 30, n. 5 (maggio 1987): 440–45. http://dx.doi.org/10.1007/bf01035292.

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12

Marshall, R. A., e F. W. Menk. "Observations of Pc 3-4 and Pi 2 geomagnetic pulsations in the low-latitude ionosphere". Annales Geophysicae 17, n. 11 (30 novembre 1999): 1397–410. http://dx.doi.org/10.1007/s00585-999-1397-2.

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Abstract. Day-time Pc 3–4 (~5–60 mHz) and night-time Pi 2 (~5–20 mHz) ULF waves propagating down through the ionosphere can cause oscillations in the Doppler shift of HF radio transmissions that are correlated with the magnetic pulsations recorded on the ground. In order to examine properties of these correlated signals, we conducted a joint HF Doppler/magnetometer experiment for two six-month intervals at a location near L = 1.8. The magnetic pulsations were best correlated with ionospheric oscillations from near the F region peak. The Doppler oscillations were in phase at two different altitudes, and their amplitude increased in proportion to the radio sounding frequency. The same results were obtained for the O- and X-mode radio signals. A surprising finding was a constant phase difference between the pulsations in the ionosphere and on the ground for all frequencies below the local field line resonance frequency, independent of season or local time. These observations have been compared with theoretical predictions of the amplitude and phase of ionospheric Doppler oscillations driven by downgoing Alfvén mode waves. Our results agree with these predictions at or very near the field line resonance frequency but not at other frequencies. We conclude that the majority of the observations, which are for pulsations below the resonant frequency, are associated with downgoing fast mode waves, and models of the wave-ionosphere interaction need to be modified accordingly.Key words. Ionosphere (ionosphere irregularities) · Magnetospheric physics (magnetosphere-ionosphere interactions) · Radio science (ionospheric physics)

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13

Gordon, W. E. "The Propagation of Radio Waves: The Theory of Radio Waves of Low Power in the Ionosphere and Magnetosphere". Eos, Transactions American Geophysical Union 68, n. 12 (1987): 164. http://dx.doi.org/10.1029/eo068i012p00164-03.

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14

Rycroft, M. J. "The Propagation of Radio Waves: the Theory of Radio Waves of Low Power in the Ionosphere and Magnetosphere". Physics of the Earth and Planetary Interiors 43, n. 3 (settembre 1986): 255–57. http://dx.doi.org/10.1016/0031-9201(86)90054-3.

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15

Heading, J. "The Propagation of Radio Waves—The Theory of Radio Waves of Low Power in the Ionosphere and Magnetosphere". Journal of Atmospheric and Terrestrial Physics 48, n. 4 (aprile 1986): 415–16. http://dx.doi.org/10.1016/0021-9169(86)90009-7.

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16

Mingaleva, G. I., V. S. Mingalev e I. V. Mingalev. "Simulation study of the high-latitude F-layer modification by powerful HF waves with different frequencies for autumn conditions". Annales Geophysicae 21, n. 8 (31 agosto 2003): 1827–38. http://dx.doi.org/10.5194/angeo-21-1827-2003.

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Abstract. The large-scale high-latitude F-region modification by high power radio waves is investigated using a numerical model of the convecting high-latitude ionosphere developed earlier. Simulations are performed for the point with geographic coordinates of the ionospheric heater near Tromsø, Scandinavia for autumn conditions. The calculations are made for distinct cases, in which high power waves have different frequencies, both for nocturnal and for day-time conditions. The results of modeling indicate that the frequency of HF waves ought to influence significantly the large-scale F-region modification by high power radio waves in the high-latitude ionosphere.Key words. Ionosphere (active experiments; modeling and forecasting; plasma temperature and density)

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17

Afanasiev, Nikolay, e Stanislav Chudaev. "DIAGNOSTICS OF THE STOCHASTIC IONOSPHERIC CHANNEL IN THE DECAMETER BAND OF RADIO WAVES". Solnechno-Zemnaya Fizika 6, n. 4 (22 dicembre 2020): 77–85. http://dx.doi.org/10.12737/szf-64202010.

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We propose a method for direct diagnostics of a stochastic ionospheric radio channel. This method can recalculate probe signal characteristics into transmitted signal characteristics. We derive analytical equations of second-order statistical moments for trajectory characteristics of the main and probe signals propagating in a three-dimensional randomly inhomogeneous ionosphere. We take into account boundary conditions at signal transmission and reception points. As a model of random irregularities of permittivity of the ionosphere, we utilize the concept of a changing space-time correlation ellipsoid, which is self-consistent with spatial changes in the average ionosphere. Time fluctuations of random irregularities are taken into account by the hypothesis of frozen transfer. We use analytical relationships to calculate the expected statistical characteristics of decameter signals along oblique probing paths of the ionosphere. An operational numerical algorithmization of the formulas derived is proposed. We report results of numerical experiments to determine the expected phase variances, group delay, and Doppler frequency shift of the main signal on a given single-hop path, based on measurements of these characteristics of a probe signal on a secondary path. We demonstrate the efficiency of the proposed method for diagnosing statistical trajectory characteristics of a decameter signal along single-hop paths under conditions when ground points of transmission and reception of the main and probe signals are outside the vicinity of focusing points of the wave field.

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18

Afanasiev, Nikolay, e Stanislav Chudaev. "DIAGNOSTICS OF THE STOCHASTIC IONOSPHERIC CHANNEL IN THE DECAMETER BAND OF RADIO WAVES". Solar-Terrestrial Physics 6, n. 4 (22 dicembre 2020): 66–73. http://dx.doi.org/10.12737/stp-64202010.

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Abstract (sommario):

We propose a method for direct diagnostics of a stochastic ionospheric radio channel. This method can recalculate probe signal characteristics into transmitted signal characteristics. We derive analytical equations of second-order statistical moments for trajectory characteristics of the main and probe signals propagating in a three-dimensional randomly inhomogeneous ionosphere. We take into account boundary conditions at signal transmission and reception points. As a model of random irregularities of permittivity of the ionosphere, we utilize the concept of a changing space-time correlation ellipsoid, which is self-consistent with spatial changes in the average ionosphere. Time fluctuations of random irregularities are taken into account by the hypothesis of frozen transfer. We use analytical relationships to calculate the expected statistical characteristics of decameter signals along oblique probing paths of the ionosphere. An operational numerical algorithmization of the formulas derived is proposed. We report results of numerical experiments to determine the expected phase variances, group delay, and Doppler frequency shift of the main signal on a given single-hop path, based on measurements of these characteristics of a probe signal on a secondary path. We demonstrate the efficiency of the proposed method for diagnosing statistical trajectory characteristics of a decameter signal along single-hop paths under conditions when ground points of transmission and reception of the main and probe signals are outside the vicinity of focusing points of the wave field.

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19

Bakhmetieva, Nataliya V., Gennady I. Grigoriev, Ariadna V. Tolmacheva e Ilia N. Zhemyakov. "Investigations of Atmospheric Waves in the Earth Lower Ionosphere by Means of the Method of the Creation of the Artificial Periodic Irregularities of the Ionospheric Plasma". Atmosphere 10, n. 8 (6 agosto 2019): 450. http://dx.doi.org/10.3390/atmos10080450.

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We present results of the studies of internal gravity waves based on altitude-time dependences of the temperature and the density of the neutral component and the velocity of the vertical plasma motion at altitudes of the lower ionosphere (60–130 km). The vertical plasma velocity, which in the specified altitude range is equal to the velocity of the neutral component, the temperature, and the density of the neutral atmosphere are determined by the method of the resonant scattering of radio waves by artificial periodic irregularities (APIs) of the ionosphere plasma. We have developed an API technique and now we are evolving it for studying the ionosphere and the neutral atmosphere using the Sura heating facility (56.1 N; 46.1 E), Nizhny Novgorod, Russia. An advantage of the API technique is the opportunity to determine the parameters of the undisturbed natural environment under a disturbance of the ionosphere by a field of powerful high frequency radio waves. Analysis of altitude-time variations of the neutral temperature, the density, and the vertical plasma velocity allows one to estimate periods of atmospheric waves propagation. Wavelike variations with a period from 5 min to 3 h and more are clearly determined.

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20

Nagai, Ken, Kenji Ohta, Yasuhide Hobara e Masashi Hayakawa. "Transmission characteristics of VLF/ELF radio waves through the Jovian ionosphere". Geophysical Research Letters 20, n. 22 (19 novembre 1993): 2435–38. http://dx.doi.org/10.1029/93gl02845.

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21

Chernogor, L. F., V. L. Frolov e V. F. Pushin. "Infrasound oscillations in the ionosphere affected by high-power radio waves". Radiophysics and Quantum Electronics 55, n. 5 (ottobre 2012): 296–308. http://dx.doi.org/10.1007/s11141-012-9369-x.

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22

Shi, Jiankui, Zheng Wang, Wei Tao, G. A. Zherebtsov, E. B. Romanova e K. G. Ratovsky. "Investigation of Total Absorption of Radio Waves in High Latitude Ionosphere". Plasma Science and Technology 16, n. 9 (settembre 2014): 833–36. http://dx.doi.org/10.1088/1009-0630/16/9/05.

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23

Bakhmetieva, N. V., V. L. Frolov, V. D. Vyakhirev, E. E. Кalinina, A. D. Akchurin e E. Yu Zykov. "The lower ionosphere response to its disturbances by powerful radio waves". Advances in Space Research 61, n. 7 (aprile 2018): 1919–30. http://dx.doi.org/10.1016/j.asr.2017.07.022.

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24

Liu, Moran, Chen Zhou, Xiang Wang, Bin Bin Ni e Zhengyu Zhao. "Numerical simulation of oblique ionospheric heating by powerful radio waves". Annales Geophysicae 36, n. 3 (13 giugno 2018): 855–66. http://dx.doi.org/10.5194/angeo-36-855-2018.

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<p><strong>Abstract.</strong> In this paper, we investigate the ionospheric heating by oblique incidence of powerful high-frequency (HF) radio waves using three-dimensional numerical simulations. The ionospheric electron density and temperature perturbations are examined by incorporating the ionospheric electron transport equations and ray-tracing algorithm. The energy distribution of oblique incidence heating waves in the ionosphere is calculated by the three-dimensional ray-tracing algorithm. The calculation takes into consideration the electric field of heating waves in the caustic region by the plane wave spectral integral method. The simulation results show that the ionospheric electron density and temperature can be disturbed by oblique incidence of powerful radio waves, especially in the caustic region of heating waves. The oblique ionospheric heating with wave incidence parallel and perpendicular to the geomagnetic field in the mid-latitude ionosphere is explored by simulations, results of which indicate that the ionospheric modulation is more effective when the heating wave propagates along the magnetic field line. Ionospheric density and temperature striations in the caustic region due to thermal self-focusing instability are demonstrated, as well as the time evolution of the corresponding fluctuation spectra.</p>

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25

Liu, Lingxiao, Tian Lu, Mingxue Gong e Wuyu Zhang. "Study on the strength loss of Multi-hop HF Radio Propagation". MATEC Web of Conferences 175 (2018): 03012. http://dx.doi.org/10.1051/matecconf/201817503012.

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The reflections of high frequency (HF) radio waves between ionosphere and earth’s surface make long-distance information transmission possible. In this paper, the propagation process of radio signals was analyzed and the ionosphere was simplified. Considering the strength loss of signals that occurs in the travelling process and at the reflection points, two pairs of differential equations and integral equations were established to simulate the strength variations of HF radio waves and noises. A different equation of SNR was also developed, which utilized the failure threshold of signal-noise-ratio (SNR) as a criterion to evaluate the effectiveness of signals. Meanwhile, the pace of SNR attenuation was simulated when reflections happens on calm ocean, turbulent ocean, smooth terrain and rugged terrain.

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Mingaleva, G. I., V. S. Mingalev e O. V. Mingalev. "Simulation study of the large-scale modification of the mid-latitude F-layer by HF radio waves with different powers". Annales Geophysicae 30, n. 8 (17 agosto 2012): 1213–22. http://dx.doi.org/10.5194/angeo-30-1213-2012.

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Abstract. A mathematical model of the ionosphere, developed earlier, is applied to investigate the large-scale mid-latitude F-layer modification by HF radio waves with different powers. Simulations are performed for the point with geographic coordinates of the "Sura" heating facility (Nizhny Novgorod, Russia) for autumn conditions. The calculations are made for distinct cases, in which the effective absorbed power has different values belonging to the 5–100 MW range, both for nocturnal and daytime conditions. The frequency of powerful HF waves is chosen to be close to the most effective frequency for the large-scale F2-layer modification. The results of modeling indicate that the effective absorbed power can influence considerably the F-layer response to high-power radio waves in the mid-latitude ionosphere.

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27

Kuo, S. P., e E. Koretzky. "Generation of density irregularities and whistler waves by powerful radio waves in the polar ionosphere". Physics of Plasmas 8, n. 1 (gennaio 2001): 277–84. http://dx.doi.org/10.1063/1.1334610.

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Uryadov, V. P., G. G. Vertogradov, V. G. Vertogradov, G. P. Komrakov, Yu N. Cherkashin e V. V. Vas’kov. "Field-aligned scattering of HF radio waves under conditions of action of high-power oblique radio waves on the ionosphere". Radiophysics and Quantum Electronics 50, n. 8 (agosto 2007): 611–18. http://dx.doi.org/10.1007/s11141-007-0053-5.

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Pavelyev, A. G., K. Zhang, J. Wickert, T. Schmidt, Y. A. Liou, V. N. Gubenko, A. A. Pavelyev, R. R. Salimzjanov e Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques Discussions 4, n. 2 (1 marzo 2011): 1465–92. http://dx.doi.org/10.5194/amtd-4-1465-2011.

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Abstract. Conditions for communication, navigation, and remote sensing in the ionosphere and atmosphere depend strongly on the ionospheric impact on the radio waves propagation. By use of the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data a description of different types of the ionospheric contributions to the RO signals at the altitudes 30–90 km of the RO ray perigee is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz. An analytical model is introduced for description of the radio waves propagation in a stratified medium consisting of sectors having the spherically symmetric distributions of refractivity. Model presents analytical expressions for the phase path and refractive attenuation of radio waves. Model is applied for analysis of the radio waves propagation effects along a prolonged path including the atmosphere and two parts of the ionosphere. Model explains significant amplitude and phase variations at the altitudes 30–90 km of the RO ray perigee as connected with influence of the inclined ionospheric layers. An innovative eikonal acceleration technique is described and applied for the identification of the inclined ionospheric layers contributions and their location. Possibility to separate the influence of layered structures from contributions of irregularities and turbulence is analyzed.

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Witvliet, Ben A., Rosa M. Alsina-Pagès, Erik van Maanen e Geert Jan Laanstra. "Design and Validation of Probes and Sensors for the Characterization of Magneto-Ionic Radio Wave Propagation on Near Vertical Incidence Skywave Paths". Sensors 19, n. 11 (9 giugno 2019): 2616. http://dx.doi.org/10.3390/s19112616.

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This article describes the design and validation of deployable low-power probes and sensors to investigate the influence of the ionosphere and the Earth’s magnetic field on radio wave propagation below the plasma frequency of the ionosphere, known as Near Vertical Incidence Skywave (NVIS) propagation. The propagation of waves that are bent downward by the ionosphere is dominated by a bi-refractive mechanism called ‘magneto-ionic propagation’. The polarization of both downward waves depends on the spatial angle between the Earth’s magnetic field and the direction of propagation of the radio wave. The probes and sensors described in this article are needed to simultaneously investigate signal fading and polarization dynamics on six radio wave propagation paths. The 1-Watt probes realize a 57 dB signal-to-noise ratio. The probe polarization is controlled using direct digital synthesis and the cross-polarization is 25–35 dB. The intermodulation-free dynamic range of the sensor exceeds 100 dB. Measurement speed is 3000 samples/second. This publication covers design, practical realization and deployment issues. Research performed with these devices will be shared in subsequent publications.

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Chernyshev, A., A. Kosov, M. Mogilevsky, D. Chugunin, V. Munitsyn, M. Dolgonosov e D. Skulachev. "Space Experiment on Measuring Ionospheric Signal Delay RWIS (Radio Waves Ionosphere Sensing)". Исследования Земли из космоса, n. 6 (dicembre 2018): 13–23. http://dx.doi.org/10.31857/s020596140003364-1.

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Gurevich, A. V., e G. M. Milikh. "Artificial airglow due to modifications of the ionosphere by powerful radio waves". Journal of Geophysical Research: Space Physics 102, A1 (1 gennaio 1997): 389–94. http://dx.doi.org/10.1029/96ja02916.

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Naumov, N. D. "On the demodulation of short radio waves propagating through the lower ionosphere". Plasma Physics Reports 38, n. 13 (dicembre 2012): 1012–15. http://dx.doi.org/10.1134/s1063780x12080211.

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Robinson, T. R. "The heating of the high lattitude ionosphere by high power radio waves". Physics Reports 179, n. 2-3 (luglio 1989): 79–209. http://dx.doi.org/10.1016/0370-1573(89)90005-7.

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Фролов, Владимир, e Vladimir Frolov. "Spatial structure of plasma density perturbations, induced in the ionosphere modified by powerful HF radio waves: review of experimental results". Solnechno-Zemnaya Fizika 1, n. 2 (17 giugno 2015): 22–48. http://dx.doi.org/10.12737/10383.

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In the review, the results of experimental studies of spatial structure of small-, middle-, and large-scale plasma density perturbations induced in the ionosphere by its pumping by powerful HF O-mode (ordinary) radio waves, are analyzed. It is shown that the region with induced plasma density perturbations occupied all ionosphere body from its E-region up to the topside ionosphere in the height and it has the horizontal length of about of 300–500 km. Peculiarities of generation of artificial ionosphere irregularities of different scale-lengths in the magnetic zenith region are stated. Experimental results obtained under conditions of iono-sphere periodical pumping when the generation of travel ionosphere disturbances is revealed are also discussed.

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36

Ostapenko, A. A., E. E. Titova, A. P. Nickolaenko, T. Turunen, J. Manninen e T. Raita. "Characteristics of VLF atmospherics near the resonance frequency of the Earth-ionosphere waveguide 1.6–2.3 kHz by observations in the auroral region". Annales Geophysicae 28, n. 1 (20 gennaio 2010): 193–202. http://dx.doi.org/10.5194/angeo-28-193-2010.

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Abstract. Recordings of ELF-VLF waves with the right-hand (RH) and the left-hand (LH) circular polarization were made in Northern Finland. Analysis showed a difference between the RH and LH polarized waves. A pronounced maximum of the wave amplitude was observed at the first critical frequency of the Earth-ionosphere waveguide (the first transverse resonance) around 1.6–2.3 kHz. The wave had the circular LH polarization at this maximum. To interpret observations, we computed the characteristics of the waveguide modes by using the full wave solution in the night model of the ionosphere. Computations show that the spectral maximum at the first transverse resonance frequency arises from a small absorption of the LH polarized radio wave in the magnetized ionosphere plasma, forming the upper boundary of the Earth-ionosphere waveguide.

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37

Rogov, D. D., V. M. Vystavnoi, N. F. Blagoveshchenskaya, P. E. Baryshev e A. S. Kalishin. "RUSSIAN HIGH-LATITUDE NETWORK OF OBLIQUE IONOSPHERIC SOUNDING". Meteorologiya i Gidrologiya, n. 4 (2021): 5–13. http://dx.doi.org/10.52002/0130-2906-2021-4-5-13.

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The network for monitoring the high-latitude ionosphere by the method of oblique ionospheric sounding deployed in the Russian Arctic region is considered. The study describes the main results of operational data processing for studying the high-latitude ionosphere and determining the conditions for the optimum operation of radio communication systems and over-the-horizon radars in this region. The study demonstrates the potential of the network as a tool for the remote diagnostics of parameters of small-scale artificial ionospheric irregularities induced by powerful HF radio waves in the mid-latitude ionospheric F-region.

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38

Fejer, J. A. "The Propagation of Radio Waves: The Theory of Radio Waves of Low Power in the Ionosphere and Magnetosphere (K. G. Budden)". SIAM Review 30, n. 2 (giugno 1988): 327. http://dx.doi.org/10.1137/1030067.

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39

Sinha, A. K., B. M. Pathan, R. Rajaram e D. R. K. Rao. "Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations". Annales Geophysicae 20, n. 1 (31 gennaio 2002): 69–80. http://dx.doi.org/10.5194/angeo-20-69-2002.

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Abstract. Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI) for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip), Mumbai (13.4° N dip) and Ujjain (18.6° N dip) exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not inconsistent with our observations.Key words. Magnetospheric physics (magnetosphere – ionosphere interactions) Ionosphere (ionosphere – magnetoshere interactions; ionospheric irregularities)

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40

Blagoveshchenskaya, N. F., T. D. Borisova, V. A. Kornienko, B. Thidé, M. T. Rietveld, M. J. Kosch e T. Bösinger. "Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere". Annales Geophysicae 23, n. 1 (31 gennaio 2005): 87–100. http://dx.doi.org/10.5194/angeo-23-87-2005.

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Abstract. Experimental results from three ionospheric HF pumping experiments in overdense E or F regions are summarized. The experiments were conducted by the use of the EISCAT HF Heating facility located near Tromsø, Norway, allowing HF pumping the ionosphere in a near geomagnetic field-aligned direction. Distinctive features related to auroral activations in the course of the experiments are identified. Typical features observed in all experiments are the following: generation of scattered components in dynamic HF radio scatter Doppler spectra; strong increase of ion temperatures Ti and local ionospheric electric field E0; modification of the auroral arc and local spiral-like formation. However, some effects were observed only when the HF pump wave was reflected from the F2 layer. Among them are the generation of intense field-aligned ion outflows, and a strong increase in the electron temperature Te with altitude. A possible scenario for the substorm triggering due to HF pumping into an auroral ionosphere is discussed. The authors present their interpretation of the data as follows. It is suggested that two populations of charged particles are at play. One of them is the runaway population of electrons and ions from the ionosphere caused by the effects of the powerful HF radio wave. The other is the population of electrons that precipitate from the magnetosphere. It is shown that the hydrodynamical equilibrium was disrupted due to the effects of the HF pumping. We estimate that the parallel electric field can reach values of the order of 30mV/m during substorm triggering.

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41

Губенко, Владимир, Vladimir Gubenko, Иван Кириллович e Ivan Kirillovich. "Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere". Solnechno-Zemnaya Fizika 5, n. 3 (30 settembre 2019): 116–29. http://dx.doi.org/10.12737/szf-53201912.

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We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.

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42

Губенко, Владимир, Vladimir Gubenko, Иван Кириллович e Ivan Kirillovich. "Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere". Solar-Terrestrial Physics 5, n. 3 (30 settembre 2019): 98–108. http://dx.doi.org/10.12737/stp-53201912.

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Abstract (sommario):

We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.

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43

Yeang, Chen-Pang. "From Mechanical Objectivity to Instrumentalizing Theory: Inventing Radio Ionospheric Sounders". Historical Studies in the Natural Sciences 42, n. 3 (1 giugno 2012): 190–234. http://dx.doi.org/10.1525/hsns.2012.42.3.190.

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While the discovery of the ionosphere through wireless communications technology in the mid-1920s had built a close connection between atmospheric science and radio, the full-fledged use of radio waves as a geophysical probe did not start until an instrumental development occurred a few years later. This article examines this advance, which centered on the invention of radio sounders of the ionosphere. Like the earlier radio experiments on the ionosphere, the sounders bounced radio waves off the upper atmosphere and inferred its properties from the returns. But the new apparatuses contained valuable innovations. In the 1930s, researchers at American Telephone and Telegraph Company (AT&T), Britain's Radio Research Board (RRB), the Technical University of Munich, and the U.S. National Bureau of Standards (NBS) automated data recording with oscilloscopic displays and inscription gadgets. They also devised control mechanisms to synchronize the acquisition of data with the change of transmitting signals. On the one hand, such automation was consistent with Lorraine Daston and Peter Galison's "mechanical objectivity," which minimizes human interference, makes experiments repeatable, and reduces personal equations, most notably perhaps with the Bureau of Standards' automatic single-frequency sounder. On the other hand, however, the automation also embodied mechanically theory-laden experimental procedures—it instrumentalized a theory that underlay the experimental scheme. The British and Americans' sweep-frequency recorder reckoned precisely the mandate of the magneto-ionic theory, the dominant model of radio-wave propagation. The sweep-frequency recorder incorporated the magneto-ionic theory by producing an easy-to-measure critical condition that the theory had predicted.

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44

Пономарчук, Сергей, Sergey Ponomarchuk, Галина Котович, Galina Kotovich, Елена Романова, Elena Romanova, Анатолий Тащилин e Anatoliy Tashchilin. "Forecasting characteristics of propagation of decameter radio waves using the global ionosphere and plasmasphere model". Solnechno-Zemnaya Fizika 1, n. 3 (27 settembre 2015): 49–54. http://dx.doi.org/10.12737/10452.

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We present the forecast results of maximal usable frequencies for mid-latitude paths on the base of complex We present the results of forecasting maximum usable frequencies (MUF) on middle-latitude paths on the basis of complex algorithm including modules of the ionosphere and plasmasphere global model (IPGM) and the model of radio wave propagation. The computation of propagation characteristics for decameter radio waves is carried out within the framework of normal wave technique. IPGM developed in ISTP SB RAS enables to compute electron concentration profiles and effective frequency of collisions using minimum number of input data and taking into account physical processes in the Earth’s upper atmosphere. To estimate the efficiency of using IPGM in long-term forecast of radio wave propagation we computed MUF for radio communication in various heliogeophysical conditions. To obtain precision characteristics of MUF forecast we used experimental data of oblique sounding on Magadan–Irkutsk, Khabarovsk–Irkutsk, Norilsk–Irkutsk paths. The paths are equipped with modern ionosphere diagnostic hardware for oblique sounding by continuous chirp signal. We also compared results of MUF forecast using IPGM with computations carried out according IRI model.

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45

Романова, Elena Romanova, Котович, Galina Kotovich, Пономарчук, Sergey Ponomarchuk, Тащилин e Anatoliy Tashchilin. "Forecasting characteristics of propagation of decameter radio waves using the global ionosphere and plasmasphere model". Solar-Terrestrial Physics 1, n. 3 (27 settembre 2015): 49–54. http://dx.doi.org/10.12737/11452.

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Abstract (sommario):

We present the forecast results of maximal usable frequencies for mid-latitude paths on the base of complex We present the results of forecasting maximum usable frequencies (MUF) on middle-latitude paths on the basis of complex algorithm including modules of the ionosphere and plasmasphere global model (IPGM) and the model of radio wave propagation. The computation of propagation characteristics for decameter radio waves is carried out within the framework of normal wave technique. IPGM developed in ISTP SB RAS enables to compute electron concentration profiles and effective frequency of collisions using minimum number of input data and taking into account physical processes in the Earth’s upper atmosphere. To estimate the efficiency of using IPGM in long-term forecast of radio wave propagation we computed MUF for radio communication in various heliogeophysical conditions. To obtain precision characteristics of MUF forecast we used experimental data of oblique sounding on Magadan–Irkutsk, Khabarovsk–Irkutsk, Norilsk–Irkutsk paths. The paths are equipped with modern ionosphere diagnostic hardware for oblique sounding by continuous chirp signal. We also compared results of MUF forecast using IPGM with computations carried out according IRI model.

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46

Molchanov, O., E. Fedorov, A. Schekotov, E. Gordeev, V. Chebrov, V. Surkov, A. Rozhnoi et al. "Lithosphere-atmosphere-ionosphere coupling as governing mechanism for preseismic short-term events in atmosphere and ionosphere". Natural Hazards and Earth System Sciences 4, n. 5/6 (22 novembre 2004): 757–67. http://dx.doi.org/10.5194/nhess-4-757-2004.

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Abstract. We present a general concept of mechanisms of preseismic phenomena in the atmosphere and ionosphere. After short review of observational results we conclude: 1. Upward migration of fluid substrate matter (bubble) can lead to ousting of the hot water/gas near the ground surface and cause an earthquake (EQ) itself in the strength-weakened area; 2. Thus, time and place of the bubble appearance could be random values, but EQ, geochemistry anomaly and foreshocks (seismic, SA and ULF electromagnetic ones) are casually connected; 3. Atmospheric perturbation of temperature and density could follow preseismic hot water/gas release resulting in generation of atmospheric gravity waves (AGW) with periods in a range of 6–60min; 4. Seismo-induced AGW could lead to modification of the ionospheric turbulence and to the change of over-horizon radio-wave propagation in the atmosphere, perturbation of LF waves in the lower ionosphere and ULF emission depression at the ground.

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47

Nikolaenko, A. P. "Scattering of elf radio waves on global inhomogeneities of the earth-ionosphere cavity". Radiophysics and Quantum Electronics 29, n. 1 (gennaio 1986): 26–32. http://dx.doi.org/10.1007/bf01033999.

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48

Tokar', V. G., L. I. Rubinshtein e M. A. Nikitin. "Depolarization of short-wave radio waves in the ionosphere in the quasiisotropic approximation". Radiophysics and Quantum Electronics 30, n. 1 (gennaio 1987): 29–33. http://dx.doi.org/10.1007/bf01034071.

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49

Gurevich, A., H. Carlson, M. Kelley, T. Hagfors, A. Karashtin e K. Zybin. "Nonlinear structuring of the ionosphere modified by powerful radio waves at low latitudes". Physics Letters A 251, n. 5 (febbraio 1999): 311–21. http://dx.doi.org/10.1016/s0375-9601(98)00786-5.

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50

Borisov, N. "Excitation of a drift instability in the ionosphere illuminated by powerful radio waves". Physics Letters A 330, n. 1-2 (settembre 2004): 107–12. http://dx.doi.org/10.1016/j.physleta.2004.07.014.

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