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Journal articles on the topic 'Ionospheric electron density – South Africa'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Yao, Y. B., P. Chen, S. Zhang, and J. J. Chen. "Temporal and spatial variations in ionospheric electron density profiles over South Africa during strong magnetic storms." Natural Hazards and Earth System Sciences 13, no. 2 (2013): 375–84. http://dx.doi.org/10.5194/nhess-13-375-2013.

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Abstract. Observations from the South African TrigNet global navigation satellite system (GNSS) and vertical total electron content (VTEC) data from the Jason-1 satellite were used to analyze the variations in ionospheric electron density profiles over South Africa before and after the severe geomagnetic storms on 15 May 2005. Computerized ionospheric tomography (CIT) was used to inverse the 3-D structure of ionospheric electron density and its response to the magnetic storms. Inversion results showed that electron density significantly increased at 10:00 UT, 15 May compared with that at the s

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2

Sibanda, P., and L. A. McKinnell. "Topside ionospheric vertical electron density profile reconstruction using GPS and ionosonde data: possibilities for South Africa." Annales Geophysicae 29, no. 2 (2011): 229–36. http://dx.doi.org/10.5194/angeo-29-229-2011.

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Abstract. Successful empirical modeling of the topside ionosphere relies on the availability of good quality measured data. The Alouette, ISIS and Intercosmos-19 satellite missions provided large amounts of topside sounder data, but with limited coverage of relevant geophysical conditions (e.g., geographic location, diurnal, seasonal and solar activity) by each individual mission. Recently, methods for inferring the electron density distribution in the topside ionosphere from Global Positioning System (GPS)-based total electron content (TEC) measurements have been developed. This study is focu

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3

Altadill, David, Antoni Segarra, Estefania Blanch, et al. "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 detec

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Savas, Caner, and Fabio Dovis. "The Impact of Different Kernel Functions on the Performance of Scintillation Detection Based on Support Vector Machines." Sensors 19, no. 23 (2019): 5219. http://dx.doi.org/10.3390/s19235219.

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Scintillation caused by the electron density irregularities in the ionospheric plasma leads to rapid fluctuations in the amplitude and phase of the Global Navigation Satellite Systems (GNSS) signals. Ionospheric scintillation severely degrades the performance of the GNSS receiver in the signal acquisition, tracking, and positioning. By utilizing the GNSS signals, detecting and monitoring the scintillation effects to decrease the effect of the disturbing signals have gained importance, and machine learning-based algorithms have been started to be applied for the detection. In this paper, the pe

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Okoh, D. I., L. A. McKinnell, and P. J. Cilliers. "Developing an ionospheric map for South Africa." Annales Geophysicae 28, no. 7 (2010): 1431–39. http://dx.doi.org/10.5194/angeo-28-1431-2010.

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Abstract. The development of a map of the ionosphere over South Africa is presented in this paper. The International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were combined within their own limitations to develop an accurate representation of the South African ionosphere. The map is essentially in the form of a computer program that shows spatial and temporal representations of the South African ionosphere for a given set of geophysical parameters. A validation of the map is att

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Jin, Shuanggen, J. U. Park, J. L. Wang, B. K. Choi, and P. H. Park. "Electron Density Profiles Derived From Ground-Based GPS Observations." Journal of Navigation 59, no. 3 (2006): 395–401. http://dx.doi.org/10.1017/s0373463306003821.

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Nowadays GPS is widely used to monitor the ionosphere. However, the current results from ground-based GPS observations only provide some information on the horizontal structure of the ionosphere, and are extremely restricted in mapping its vertical structure. In this paper, tomography reconstruction technique was used to image 3D ionospheric structure with ground-based GPS. The first result of the 3D images of the ionospheric electron density distribution in South Korea has been generated from the permanent Korean GPS Network (KGN) data. Compared with the profiles obtained by independent ionos

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7

van de Heyde, V. P., C. P. Price, and D. M. Moeketsi. "Effects of mid-latitude geomagnetic storms on ionospheric Total Electron Content over South Africa." South African Journal of Geology 119, no. 1 (2016): 135–46. http://dx.doi.org/10.2113/gssajg.119.1.135.

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8

Ackermann, E. R., J. P. de Villiers, and P. J. Cilliers. "Nonlinear dynamic systems modeling using Gaussian processes: Predicting ionospheric total electron content over South Africa." Journal of Geophysical Research: Space Physics 116, A10 (2011): n/a. http://dx.doi.org/10.1029/2010ja016375.

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9

Lin, C. H., J. T. Lin, C. H. Chen, et al. "Ionospheric shock waves triggered by rockets." Annales Geophysicae 32, no. 9 (2014): 1145–52. http://dx.doi.org/10.5194/angeo-32-1145-2014.

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Abstract. This paper presents a two-dimensional structure of the shock wave signatures in ionospheric electron density resulting from a rocket transit using the rate of change of the total electron content (TEC) derived from ground-based GPS receivers around Japan and Taiwan for the first time. From the TEC maps constructed for the 2009 North Korea (NK) Taepodong-2 and 2013 South Korea (SK) Korea Space Launch Vehicle-II (KSLV-II) rocket launches, features of the V-shaped shock wave fronts in TEC perturbations are prominently seen. These fronts, with periods of 100–600 s, produced by the propul

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10

He, Y., D. Yang, J. Qian, and M. Parrot. "Response of the ionospheric electron density to different types of seismic events." Natural Hazards and Earth System Sciences 11, no. 8 (2011): 2173–80. http://dx.doi.org/10.5194/nhess-11-2173-2011.

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Abstract. The electron density data recorded by the Langmuir Probe Instrument (ISL, Instrument Sonde de Langmuir) onboard the DEMETER satellite have been collected for nearly 4 yr (during 2006–2009) to perform a statistical analysis. During this time, more than 7000 earthquakes with a magnitude larger than or equal to 5.0 occurred all over the world. For the statistical studies, all these events have been divided into various categories on the basis of the seismic information, including Southern or Northern Hemisphere earthquakes, inland or sea earthquakes, earthquakes at different magnitude l

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Norberg, J., L. Roininen, A. Kero, et al. "Sodankylä ionospheric tomography dataset 2003–2014." Geoscientific Instrumentation, Methods and Data Systems Discussions 5, no. 2 (2015): 385–404. http://dx.doi.org/10.5194/gid-5-385-2015.

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Abstract. Sodankylä Geophysical Observatory has been operating a tomographic receiver network and collecting the produced data since 2003. The collected dataset consists of phase difference curves measured from Russian COSMOS dual-frequency (150/400 MHz) low-Earth-orbit satellite signals, and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of the tomographic syste

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12

Tao, Dan, Jinbin Cao, Roberto Battiston, et al. "Seismo-ionospheric anomalies in ionospheric TEC and plasma density before the 17 July 2006 <i>M</i>7.7 south of Java earthquake." Annales Geophysicae 35, no. 3 (2017): 589–98. http://dx.doi.org/10.5194/angeo-35-589-2017.

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Abstract. In this paper, we report significant evidence for preseismic ionospheric anomalies in total electron content (TEC) of the global ionosphere map (GIM) and plasma density appearing on day 2 before the 17 July 2006 M7.7 south of Java earthquake. After distinguishing other anomalies related to the geomagnetic activities, we found a temporal precursor around the epicenter on day 2 before the earthquake (15 July 2006), which agrees well with the spatial variations in latitude–longitude–time (LLT) maps. Meanwhile, the sequences of latitude–time–TEC (LTT) plots reveal that the TECs on epicen

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Norberg, Johannes, Lassi Roininen, Antti Kero, et al. "Sodankylä ionospheric tomography data set 2003–2014." Geoscientific Instrumentation, Methods and Data Systems 5, no. 1 (2016): 263–70. http://dx.doi.org/10.5194/gi-5-263-2016.

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Abstract. Sodankylä Geophysical Observatory has been operating a receiver network for ionospheric tomography and collecting the produced data since 2003. The collected data set consists of phase difference curves measured from COSMOS navigation satellites from the Russian Parus network (Wood and Perry, 1980) and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of t

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14

Edemskiy, Ilya, Jan Lastovicka, Dalia Buresova, John Bosco Habarulema, and Ivan Nepomnyashchikh. "Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015." Annales Geophysicae 36, no. 1 (2018): 71–79. http://dx.doi.org/10.5194/angeo-36-71-2018.

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Abstract. Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC) enhancement (LTE) in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2 h after local noon). The plumes moved wi

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15

Zhao, B., W. Wan, J. Lei, Y. Wei, Y. Sahai, and B. Reinisch. "Positive ionospheric storm effects at Latin America longitude during the superstorm of 20–22 November 2003: revisit." Annales Geophysicae 30, no. 5 (2012): 831–40. http://dx.doi.org/10.5194/angeo-30-831-2012.

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Abstract. Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS) total electron content (TEC), and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times

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Adebesin, B. O., A. B. Rabiu, O. K. Obrou, and J. O. Adeniyi. "Ionospheric Peak Electron Density and Performance Evaluation of IRI-CCIR Near Magnetic Equator in Africa During Two Extreme Solar Activities." Space Weather 16, no. 3 (2018): 230–44. http://dx.doi.org/10.1002/2017sw001729.

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17

Wu, Y. W., R. Y. Liu, B. C. Zhang, et al. "Variations of the ionospheric TEC using simultaneous measurements from the China Crustal Movement Observation Network." Annales Geophysicae 30, no. 10 (2012): 1423–33. http://dx.doi.org/10.5194/angeo-30-1423-2012.

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Abstract. Variations of the ionospheric Total Electron Content (TEC) over China are investigated using the TEC data obtained from China Crustal Movement Observation Network in the year 2004. The results show a single-peak occurred in post-noon for the diurnal variation and two peaks exit around two equinox points, respectively, for the seasonal variation. Overall, the values of TEC increased from the north to the south of China. There were small but clear longitudinal differences in both sides of the longitudes with zero magnetic declination. The intensity of the day-to-day variation of TEC wa

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18

Bolmgren, Karl, Cathryn Mitchell, Talini Pinto Jayawardena, Gary Bust, Jon Bruno, and Elizabeth Mitchell. "Tomographic imaging of a large-scale travelling ionospheric disturbance during the Halloween storm of 2003." Annales Geophysicae 38, no. 6 (2020): 1149–57. http://dx.doi.org/10.5194/angeo-38-1149-2020.

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Abstract. The most intense ionospheric storm observed in recent times occurred between 29 and 31 October 2003. The disturbances to the high-latitude regions set off several large-scale travelling ionospheric disturbances (LSTIDs), wave-like perturbations in the ionospheric electron density. This paper investigates one particular TID on 31 October 2003 using North American Global Positioning System (GPS) receiver network data and a tomographic imaging technique. The TID has an estimated period of 30 min and an estimated horizontal wavelength of 700 km and propagates south-westward over North Am

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19

Kishore, Amol, Anil Deo, and Sushil Kumar. "Upper atmospheric remote sensing using ELF – VLF lightning generated tweek and whistler sferics." South Pacific Journal of Natural and Applied Sciences 34, no. 1 (2016): 12. http://dx.doi.org/10.1071/sp16002.

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Tweek and whistler atmospherics (sferics) recorded at a low latitude station, Suva (18.2oS, 178.3oE, geomag. lat. 22.2oS, L = 1.17) Fiji, in the South Pacific region, during September 2003–July 2004 and March–December 2006 were analyzed to probe the nighttime D-region ionosphere and plasmasphere. From the first harmonic analysis of the selected 1063 tweeks, the path integrated ionospheric reflection height was estimated mostly between 75–97 km with median and standard deviation of 83.6 and 4.1 km, respectively. The path integrated mean electron density was estimated to vary from 24.4–31.5 cm–3

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20

Jeon, Min-Ho, and Chang-Heon Oh. "Analysis of Ionospheric foF2 by Solar Activity over the Korean Peninsula." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 1 (2016): 71. http://dx.doi.org/10.11591/ijece.v6i1.9344.

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The F2 layer is the upper sector of the ionospheric F region, and it is ~250 km above sea level. It has a high electron density and thus plays an important role in shortwave communications. The variations of the critical frequency of the F2 layer (foF2) offer clues regarding the events happening within the entire F2 layer, and foF2 analysis is essential for stable shortwave communications. This study analyzes the seasonal and annual variations of the foF2 as well as the reactions of the F2 layer height at two locations in South Korea by employing the mean and standard deviation (SD) used in pr

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Jeon, Min-Ho, and Chang-Heon Oh. "Analysis of Ionospheric foF2 by Solar Activity over the Korean Peninsula." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 1 (2016): 71. http://dx.doi.org/10.11591/ijece.v6i1.pp71-81.

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The F2 layer is the upper sector of the ionospheric F region, and it is ~250 km above sea level. It has a high electron density and thus plays an important role in shortwave communications. The variations of the critical frequency of the F2 layer (foF2) offer clues regarding the events happening within the entire F2 layer, and foF2 analysis is essential for stable shortwave communications. This study analyzes the seasonal and annual variations of the foF2 as well as the reactions of the F2 layer height at two locations in South Korea by employing the mean and standard deviation (SD) used in pr

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Gillies, R. G., G. C. Hussey, H. G. James, G. J. Sofko, and D. André. "Modelling and observation of transionospheric propagation results from ISIS II in preparation for ePOP." Annales Geophysicae 25, no. 1 (2007): 87–97. http://dx.doi.org/10.5194/angeo-25-87-2007.

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Abstract. The enhanced Polar Outflow Probe (ePOP) is scheduled to be launched as part of the Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer (CASSIOPE) satellite in early 2008. A Radio Receiver Instrument (RRI) on ePOP will receive HF transmissions from various ground-based transmitters. In preparation for the ePOP mission, data from a similar transionospheric experiment performed by the International Satellites for Ionospheric Studies (ISIS) II satellite has been studied. Prominent features in the received 9.303-MHz signal were periodic Faraday fading of signal intensity at rate

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Hu, L., B. Ning, L. Liu, et al. "Validation of COSMIC ionospheric peak parameters by the measurements of an ionosonde chain in China." Annales Geophysicae 32, no. 10 (2014): 1311–19. http://dx.doi.org/10.5194/angeo-32-1311-2014.

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Abstract. Although the electron density profiles (EDPs) from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurement have been validated by ionosonde data at a number of locations during the solar minimum period, the performance of COSMIC measurements at different latitudes has not been well evaluated, particularly during the solar maximum period. In this paper the COSMIC ionospheric peak parameters (peak electron density of the F region – NmF2; peak height of the F region – hmF2) are validated by the ionosonde data from an observation chain in China during

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Amabayo, Emirant Bertillas, Simon Katrini Anguma, and Edward Jurua. "Tracking the Ionospheric Response to the Solar Eclipse of November 03, 2013." International Journal of Atmospheric Sciences 2014 (October 23, 2014): 1–10. http://dx.doi.org/10.1155/2014/127859.

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The ionospheric dynamics is highly influenced by the solar radiation. During a solar eclipse, the moon occults the solar radiation from reaching the ionosphere, which may drastically affect the variability of the ionosphere. The variability of total electron content (TEC) observed by dual frequency Global Positioning System (GPS) receivers has made it possible to study effects of solar eclipse on the ionosphere. Total eclipse occurred on November 03, 2013, and the maximum amplitude was visible at Owiny in northern Uganda. Ionospheric behavior during this eclipse was analysed by using TEC data

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Pavlov, A. V., S. Fukao, and S. Kawamura. "Comparison of the measured and modeled electron densities, and electron and ion temperatures in the low-latitude ionosphere during 19-21 March 1988." Annales Geophysicae 22, no. 8 (2004): 2747–63. http://dx.doi.org/10.5194/angeo-22-2747-2004.

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Abstract. We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2 which were observed at the equatorial anomaly crest and close to the geomagnetic equator simultaneously by the Akita, Kokubunji, Yamagawa, Okinawa, Chung-Li, Manila, Vanimo, and Darwin ionospheric sounders and by the middle and upper atmosphere (MU) radar at Shigaraki (34.85°N, 136.10°E, Japan) during the 19-21 March 1988 geomagnetically quiet time period at moderate solar activity near approximately the same geomagnetic meridian of 201°. A comparison between the electron, Te, and ion, Ti, temperature

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Marshall, R. A., U. S. Inan, T. Neubert, et al. "Optical observations geomagnetically conjugate to sprite-producing lightning discharges." Annales Geophysicae 23, no. 6 (2005): 2231–37. http://dx.doi.org/10.5194/angeo-23-2231-2005.

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Abstract. Theoretical studies have predicted that large positive cloud-to-ground discharges can trigger a runaway avalanche process of relativistic electrons, forming a geomagnetically trapped electron beam. The beam may undergo pitch angle and energy scattering during its traverse of the Earth's magnetosphere, with a small percentage of electrons remaining in the loss cone and precipitating in the magnetically conjugate atmosphere. In particular, N2 1P and N2+1N optical emissions are expected to be observable. In July and August 2003, an attempt was made to detect these optical emissions, cal

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van Rensburg, H., C. A. Matthee, and C. A. Simon. "Moonshine worms (Diopatra aciculata: Onuphidae, Annelida) in the Knysna Estuary, South Africa; taxonomy and distribution." Journal of the Marine Biological Association of the United Kingdom 100, no. 6 (2020): 897–907. http://dx.doi.org/10.1017/s0025315420000740.

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AbstractMoonshine worms are a popular bait species used for fishing. The taxon was not detected during surveys of the macrobenthos conducted in Knysna in the 1940s and 1990s, and was first reported as a harvested bait species in the mid-2000s, suggesting that it appeared for the first time in the estuary in the last three decades. A previous molecular analysis identified the worms as Diopatra aciculata, a species first described from Australia. This study provides an updated detailed morphological description of D. aciculata in South Africa to facilitate future identifications and also investi

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Sotomayor-Beltran, Carlos, and Laberiano Andrade-Arenas. "Emergence of a localized total electron content enhancement during the severe geomagnetic storm of 8 September 2017." Annales Geophysicae 37, no. 2 (2019): 153–61. http://dx.doi.org/10.5194/angeo-37-153-2019.

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Abstract. In this work, the results of the analysis on total electron content (TEC) data before, during and after the geomagnetic storm of 8 September 2017 are reported. One of the responses to geomagnetic storms due to the southern vertical interplanetary magnetic field (Bz) is the enhancement of the electron density in the ionosphere. Vertical TEC (VTEC) from the Center for Orbit determination in Europe (CODE) along with a statistical method were used to identify positive and/or negative ionospheric storms in response to the geomagnetic storm of 8 September 2017. When analyzing the response

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Balthazor, R. L., and R. J. Moffett. "A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes." Annales Geophysicae 15, no. 8 (1997): 1048–56. http://dx.doi.org/10.1007/s00585-997-1048-4.

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Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged veloc

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Cabri, L. J., A. M. McDonald, C. J. Stanley, et al. "Palladosilicide, Pd2Si, a new mineral from the Kapalagulu Intrusion, Western Tanzania and the Bushveld Complex, South Africa." Mineralogical Magazine 79, no. 2 (2015): 295–307. http://dx.doi.org/10.1180/minmag.2015.079.2.08.

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AbstractPalladosilicide, Pd2Si, is a new mineral (IMA 2014-080) discovered in chromite-rich samples from the Kapalagulu intrusion, western Tanzania (30°03′51′′E 5°53′16′′S and 30°05′37′′E 5°54′26′′S) and from the UG-2 chromitite, Bushveld complex, South Africa. A total of 13 grains of palladosilicide, ranging in size from 0.7 to 39.1 μm (equivalent circle diameters), were found. Synthetic Pd2Si is hexagonal, space group P62m, with a = 6.496(5), c = 3.433(4) Å, V = 125.5(1) Å3, c:a = 0.529 with Z = 3. The strongest lines calculated from the powder pattern (Anderko and Schubert, 1953) are [d in

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Imtiaz, Nadia, Waqar Younas, and Majid Khan. "Response of the low- to mid-latitude ionosphere to the geomagnetic storm of September 2017." Annales Geophysicae 38, no. 2 (2020): 359–72. http://dx.doi.org/10.5194/angeo-38-359-2020.

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Abstract. We study the impact of the geomagnetic storm of 7–9 September 2017 on the low- to mid-latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of two SYM-H minima with values of −146 and −115 nT on 8 September at 01:08 and 13:56 UT, respectively. The study is based on the analysis of data from the Global Positioning System (GPS) stations and magnetic observatories located at different longitudinal sectors corresponding to the Pacific, Asia, Africa and the Americas during the period 4–14 September 2017. The GPS data are used to derive the global, reg

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Yang, Haiyan, Xuhai Yang, Zhe Zhang, Baoqi Sun, and Weijin Qin. "Evaluation of the Effect of Higher-Order Ionospheric Delay on GPS Precise Point Positioning Time Transfer." Remote Sensing 12, no. 13 (2020): 2129. http://dx.doi.org/10.3390/rs12132129.

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In high-precision GPS precise point positioning (PPP) time transfer, errors caused by the effect of ionosphere delay have to be corrected. Usually the ionosphere-free combinations of the pseudo code and the carrier phase is used in GPS PPP data processing, and it effectively eliminates the effect of the first-order ionospheric delay. This study quantitatively analyzes the errors caused by higher-order ionospheric (Ion2+) delays in precise PPP time transfer. Data of two 7-day test periods, including low and moderate ionospheric conditions, from 20 stations located in middle- and low-latitude, w

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Daramola, Fisayo Y., Rinus Knoetze, Antoinette Swart, and Antoinette P. Malan. "First report and molecular characterization of the dagger nematode, Xiphinema oxycaudatum (Nematoda, Dorylaimidae) from South Africa." ZooKeys 894 (December 3, 2019): 1–17. http://dx.doi.org/10.3897/zookeys.894.35281.

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Plant-parasitic nematodes of the genus Xiphinema Cobb, 1913 comprise a complex group of nematode species, some of which are important vectors of plant viruses. During a field survey to determine the soil health of an abandoned honeybush (Cyclopia genistoides) monoculture, a high density of the dagger nematode, Xiphinema oxycaudatum Lamberti &amp; Bleve-Zacheo, 1979 (Nematoda, Dorylaimidae), was observed in soil around the roots of honeybush plants in an abandoned farmland at Bereaville, an old mission station in the Western Cape province of South Africa. Soil samples were taken from the rh

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Aikio, A. T., K. Mursula, S. Buchert, et al. "Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments." Annales Geophysicae 22, no. 12 (2004): 4089–101. http://dx.doi.org/10.5194/angeo-22-4089-2004.

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Abstract. The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 RE in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110km in latitude and 50km in longitude. This constellation allowed us to study the temporal evolution of plasma with a time scale of a few minutes. Ground-based instrumentation used involved two all-sky cameras, magnetometers and the EISCAT radar. The main findings were as follows. Two auroral arcs wer

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Sasmal, Sudipta, Swati Chowdhury, Subrata Kundu, et al. "Pre-Seismic Irregularities during the 2020 Samos (Greece) Earthquake (M = 6.9) as Investigated from Multi-Parameter Approach by Ground and Space-Based Techniques." Atmosphere 12, no. 8 (2021): 1059. http://dx.doi.org/10.3390/atmos12081059.

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We present a comprehensive analysis of pre-seismic anomalies as computed from the ground and space-based techniques during the recent Samos earthquake in Greece on 30 October 2020, with a magnitude M = 6.9. We proceed with a multi-parametric approach where pre-seismic irregularities are investigated in the stratosphere, ionosphere, and magnetosphere. We use the convenient methods of acoustics and electromagnetic channels of the Lithosphere–Atmosphere–Ionosphere-Coupling (LAIC) mechanism by investigating the Atmospheric Gravity Wave (AGW), magnetic field, electron density, Total Electron Conten

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Mungufeni, Patrick, Sripathi Samireddipalle, Yenca Migoya-Orué, and Yong Ha Kim. "Modeling total electron content derived from radio occultation measurements by COSMIC satellites over the African region." Annales Geophysicae 38, no. 6 (2020): 1203–15. http://dx.doi.org/10.5194/angeo-38-1203-2020.

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Abstract. This study developed a model of total electron content (TEC) over the African region. The TEC data were obtained from radio occultation measurements done by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Data during geomagnetically quiet time (Kp < 3 and Dst > −20 nT) for the years 2008–2011 and 2013–2017 were binned according to local time, seasons, solar flux level, and geographic longitude and latitude. B splines were fitted to the binned data to obtain model coefficients. The model was validated using actual COSMIC TEC data

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Ahoua, Sylvain M., John Bosco Habarulema, Olivier K. Obrou, Pierre J. Cilliers, and Zacharie K. Zaka. "Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)." Annales Geophysicae 36, no. 5 (2018): 1161–70. http://dx.doi.org/10.5194/angeo-36-1161-2018.

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Abstract. In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which were adapted to local and storm-specific response by using the critical frequency of the F2 layer (foF2) and the propagation factor (M(3000)F2) derived from three South African ionosonde measurements, Hermanus (34.40∘ S, 19.20∘ E), Grahamstown (33.30∘ S, 26.50∘ E) and Louisvale (28.50∘ S, 21.20∘ E). The

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Iloh, Patrick, George Fanourakis, and Aurobindo Ogra. "Evaluation of Physical and Chemical Properties of South African Waste Foundry Sand (WFS) for Concrete Use." Sustainability 11, no. 1 (2019): 193. http://dx.doi.org/10.3390/su11010193.

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The foundry industry in South Africa forms one of the greatest industries in the manufacturing sector. It produces waste foundry sand (WFS) that ends up in landfill sites. Around 80% of the WFS could be utilized as a substitute for sand in concrete. The utilization of WFS will benefit the industry, as raw materials (natural sand alternative) and energy are conserved, while costs of disposal are lowered. Soil pollution, as well as water and air resources, will be minimized and the foundries’ competitiveness will be improved. In this study, the physical and chemical properties of five WFSs (two

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Pavlov, A. V., S. Fukao, and S. Kawamura. "<i>F</i>-region ionospheric perturbations in the low-latitude ionosphere during the geomagnetic storm of 25-27 August 1987." Annales Geophysicae 22, no. 10 (2004): 3479–501. http://dx.doi.org/10.5194/angeo-22-3479-2004.

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Abstract. We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2 which were observed at the equatorial anomaly crest and close to the geomagnetic equator simultaneously by the Akita, Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders and by the middle and upper atmosphere (MU) radar (34.85° N, 136.10° E) during the 25-27 August 1987 geomagnetically storm-time period at low solar activity near 201°, geomagnetic longitude. A comparison between the electron and ion temperatures measured by the MU radar and those produced by the model of the

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Meyer, Nicole A., Michelle D. Wenz, James P. S. Walsh, Steven D. Jacobsen, Andrew J. Locock, and Jeffrey W. Harris. "Goldschmidtite, (K,REE,Sr)(Nb,Cr)O3: A new perovskite supergroup mineral found in diamond from Koffiefontein, South Africa." American Mineralogist 104, no. 9 (2019): 1345–50. http://dx.doi.org/10.2138/am-2019-6937.

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Abstract Goldschmidtite is a new perovskite-group mineral (IMA No. 2018-034) with the ideal formula (K,REE,Sr)(Nb,Cr)O3. A single grain of goldschmidtite with a maximum dimension of ∼100 μm was found as an inclusion in a diamond from the Koffiefontein pipe in South Africa. In addition to the dark green and opaque goldschmidtite, the diamond contained a Cr-rich augite (websteritic paragenesis) and an intergrowth of chromite, Mg-silicate, and unidentified K-Sr-REE-Nb-oxide. Geothermobarometry of the augite indicates that the depth of formation was ∼170 km. The chemical composition of gold-schmid

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Hussien, Fayrouz, Essam Ghamry, and Adel Fathy. "A Statistical Analysis of Plasma Bubbles Observed by Swarm Constellation during Different Types of Geomagnetic Storms." Universe 7, no. 4 (2021): 90. http://dx.doi.org/10.3390/universe7040090.

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Based on the observations of Ionospheric Bubble Index (IBI) data from the Swarm mission, the characteristics of plasma bubbles are investigated during different types of geomagnetic storms recorded from 2014 to 2020. The geometrical constellation of the Swarm mission enabled us to investigate the altitudinal profile of the IBIs during different activity levels in a statistical mean. Results show that the majority of IBIs associated with moderate storms are observed at low altitudes and the probability of observing IBIs at high altitudes (Swarm-B) increases with the increase in storm level. Thi

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Rieck, B., H. Pristacz, and G. Giester. "Colinowensite, BaCuSi2O6, a new mineral from the Kalahari Manganese Field, South Africa and new data on wesselsite, SrCuSi4O10." Mineralogical Magazine 79, no. 7 (2015): 1769–78. http://dx.doi.org/10.1180/minmag.2015.079.7.04.

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AbstractA new silicate, colinowensite, BaCuSi2O6, has been found in the Wessels mine, Kalahari Manganese Field, South Africa. It is associated with effenbergerite, wesselsite, lavinskyite, scottyite, diegogattaite, as well as with pectolite, quartz, aegirine, richterite, minerals of the garnet group and a number of different manganese and iron oxides, especially hausmannite and hematite. The mineral was named for the mineral collector and finder of the new species, Colin R. Owens, of Somerset West, South Africa. Colinowensite is brittle, with uneven fracture, and the estimated Mohs hardness is

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Dahlgren, H., B. Gustavsson, B. S. Lanchester, et al. "Energy and flux variations across thin auroral arcs." Annales Geophysicae 29, no. 10 (2011): 1699–712. http://dx.doi.org/10.5194/angeo-29-1699-2011.

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Abstract. Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz) and spatial (down to tens of metres) resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independent

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Rumsey, M. S., M. D. Welch, A. R. Kampf, and J. Spratt. "Diegogattaite, Na2CaCu2Si8O20·H2O: a new nanoporous copper sheet silicate from Wessels Mine, Kalahari Manganese Fields, Republic of South Africa." Mineralogical Magazine 77, no. 8 (2013): 3155–62. http://dx.doi.org/10.1180/minmag.2013.077.8.09.

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AbstractDiegogattaite (IMA2012-096), Na2CaCu2Si8O20·H2O, is a new mineral from the Wessels mine in the Kalahari manganese fields of South Africa. It occurs as a minor phase with other copper-bearing silicates, Cu-rich pectolite, sugilite, quartz, aegirine and undifferentiated Fe-Mn oxides. Diegogattaite is pale turquoise through teal blue. It is found as sub-mm sized grains in a main crystalline patch 3–4 mm in size, and is currently known from only one sample. The mineral is transparent with a vitreous lustre and may have a good cleavage on {001}. It is brittle, with an uneven fracture and a

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Amory-Mazaudier, C., M. Le Huy, Y. Cohen, et al. "Sun-Earth System Interaction studies over Vietnam: an international cooperative project." Annales Geophysicae 24, no. 12 (2006): 3313–27. http://dx.doi.org/10.5194/angeo-24-3313-2006.

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Abstract. During many past decades, scientists from various countries have studied separately the atmospheric motions in the lower atmosphere, in the Earth's magnetic field, in the magnetospheric currents, etc. All of these separate studies lead today to the global study of the Sun and Earth connections, and as a consequence, new scientific programs (IHY- International Heliophysical Year, CAWSES- Climate and Weather in the Sun-Earth System) are defined, in order to assume this new challenge. In the past, many scientists did not have the possibility to collect data at the same time in the vario

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MAJEWSKA, ROKSANA. "Tursiocola neliana sp. nov (Bacillariophyceae) epizoic on South African leatherback sea turtles (Dermochelys coriacea) and new observations on the genus Tursiocola." Phytotaxa 453, no. 1 (2020): 1–15. http://dx.doi.org/10.11646/phytotaxa.453.1.1.

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Tursiocola, a presumably exclusively epizoic diatom genus, comprises species found on various aquatic animals such as cetaceans, manatees, and marine and freshwater turtles. The genus is characterised by linear or lanceolate valves with well-developed pseudosepta at both poles, a valvocopula with three pairs of siliceous tabs, and a butterfly-like structure extending from the central nodule on the internal side of the valve. The current study describes a novel species of Tursiocola, T. neliana Majewska sp. nov. that grows epizoically on leatherback sea turtles from the Eastern Coast of South A

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Yamamoto, M., S. Fukao, R. T. Tsunoda, R. Pfaff, and H. Hayakawa. "SEEK-2 (Sporadic-<i>E</i> Experiment over Kyushu 2) − Project Outline, and Significance." Annales Geophysicae 23, no. 7 (2005): 2295–305. http://dx.doi.org/10.5194/angeo-23-2295-2005.

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Abstract. SEEK-2 (Sporadic-E Experiment over Kyushu 2) is an observation campaign to study the spatial structure of the field-aligned irregularity (FAI) and sporadic-E(Es)-layer by means of two sounding rockets and a ground-based observation network with radars and optical instruments. The experiment was successfully conducted on 3 August 2002, with successive launches of two sounding rockets from the Uchinoura Space Center (USC) of the Japan Aerospace Exploration Agency (JAXA). The timing of the experiment was carefully selected, while intense quasi-periodic (QP) echoes were observed with two

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Origlieri, Marcus J., Robert T. Downs, Derek R. Hoffman, Mihai N. Ducea, and Jeffrey E. Post. "Marshallsussmanite, NaCaMnSi3O8(OH), a new pectolite-group mineral providing insight into hydrogen bonding in pyroxenoids." Mineralogical Magazine 85, no. 3 (2018): 444–53. http://dx.doi.org/10.1180/mgm.2018.2.

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AbstractMarshallsussmanite (IMA2013-067) is a new pyroxenoid mineral from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Marshallsussmanite has ideal formula NaCaMnSi3O8(OH) and triclinic P$\bar{1}$ symmetry. Marshallsussmanite forms vitreous pink bladed crystals to 2.1 cm. The mineral shows perfect cleavage on both {100} and {001}. The chemical composition from electron microprobe (average of 20 analyses) and inductively coupled plasma mass spectrometer analysis (average of three analyses) is Li2O 0.43, Na2O 8.06, MgO 0.08, CaO 15.33, MnO 21.79, SiO2 51.71;

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Habarulema, J. B., L. A. McKinnell, and B. D. L. Opperman. "A recurrent neural network approach to quantitatively studying solar wind effects on TEC derived from GPS; preliminary results." Annales Geophysicae 27, no. 5 (2009): 2111–25. http://dx.doi.org/10.5194/angeo-27-2111-2009.

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Abstract. This paper attempts to describe the search for the parameter(s) to represent solar wind effects in Global Positioning System total electron content (GPS TEC) modelling using the technique of neural networks (NNs). A study is carried out by including solar wind velocity (Vsw), proton number density (Np) and the Bz component of the interplanetary magnetic field (IMF Bz) obtained from the Advanced Composition Explorer (ACE) satellite as separate inputs to the NN each along with day number of the year (DN), hour (HR), a 4-month running mean of the daily sunspot number (R4) and the runnin

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Mdibi, Lusanda, Robert Van Zyl, Michael Kosch, and Jonathan Ward. "A land-based HF transmitter for ionospheric propagation studies using SuperDARN radars." Journal of Engineering, Design and Technology ahead-of-print, ahead-of-print (2021). http://dx.doi.org/10.1108/jedt-02-2020-0057.

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Purpose The purpose of this paper is to design, build and test a low power high frequency (HF) transmitter that can be received by the Super Dual Auroral Radar Network (SuperDARN) radar installed at SANAE IV, the 4th South African National Antarctic Expedition Station. It is proposed that it may be possible to do propagation studies using the radar and the fixed frequency, ground-based HF transmitter beacon. Interpretation of the measurements can be used to study the ionosphere, especially Travelling Ionospheric Disturbances, which are signatures of atmospheric gravity waves. Design/methodolog

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