Bibliography
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Found 7 entries in the Bibliography.
Showing entries from 1 through 7
2020 |
Unprecedented hemispheric asymmetries during a surprise ionospheric storm: A game of drivers Astafyeva, Elvira; Bagiya, Mala; Förster, Matthias; Nishitani, Nozomu; Published by: Journal of Geophysical Research: Space Physics Published on: |
2019 |
Game of drivers and a surprise ionospheric storm For this purpose, we use a set of space-borne (the Swarm constellation, GUVI/TIMED) and ground-based (GPS receivers, magnetometers, SuperDARN) instruments. In the Astafyeva, Elvira; Bagiya, Mala; Published by: Published on: |
2018 |
Low latitude ionospheric behavior during solar transient disturbances of solar flares and storm time penetrating electric fields comprises an important part of the Earth\textquoterights space weather. The flares enhance the electron density of the sunlit ionosphere by supplying excess solar radiation. However, the degree of these density changes is subjective if a geomagnetic storm persists simultaneously. The present case study addresses the ionospheric variations over the Indian longitudes under the combined effects of the solar flares and a geomagnetic storm during 6 to 8 September 2017 and probably the first of its kind in delineating the effects of these two over the low latitude ionosphere. The X9.3 class flare of 6 September, which occurred during non-storm conditions, produced an intense E region ionization (~500\% over the ambient). However, the total electron content response to this flare was comparatively weak. The flares on 7 and 8 September occurred during the 7\textendash8 September geomagnetic storm. Though the 8 September flare occurred with higher intensity (M8.1) and early in local time compared to the flare of 7 September (M7.3), the equatorial electrojet current enhancement was lesser on 8 September (~75\% over the ambient) than that of 7 September (~110\% over the ambient). This aspect is discussed in view of the storm time convection effects over the low latitudes during 7\textendash8 September storm. The total electron content did not respond to the flares of 7 and 8 September. This behavior is attributed to the varying center-to-limb distance of the solar active region 12673 during this period. Bagiya, Mala; Thampi, Smitha; Hui, Debrup; Sunil, A.; Chakrabarty, D.; Choudhary, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2018 YEAR: 2018   DOI: 10.1029/2018JA025496 |
2014 |
The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15\textendash16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50\% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 1016 el m-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration. Bagiya, Mala; Hazarika, Rumajyoti; Laskar, Fazlul; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2014 YEAR: 2014   DOI: 10.1002/2014JA020156 low-latitude ionosphere; neutral winds; prolonged southward IMF Bz; thermospheric neutral composition |
2011 |
Bagiya, Mala; Iyer, K.; Joshi, H.; Thampi, Smitha; Tsugawa, Takuya; Ravindran, Sudha; Sridharan, R.; Pathan, B.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011   DOI: 10.1029/2010JA015845 |
2010 |
Multitechnique studies of ionospheric phenomena The ionospheric plasma density shows temporal variability (with time of the day, season and solar cycle), latitudinal variability and variations during geomagnetic disturbances. In Published by: Published on: |
2009 |
The dual frequency signals from the GPS satellites recorded at Rajkot (22.29 N, 70.74 E, Geographic, 14.03 N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated. Bagiya, Mala; Joshi, H.; Iyer, K.; Aggarwal, M.; Ravindran, S.; Pathan, B.; Published by: Annales Geophysicae Published on: Jan-01-2009 YEAR: 2009   DOI: 10.5194/angeo-27-1047-2009 |
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