Bibliography

Distinct ionospheric response to three different geomagnetic storms during 2016 using GPS-TEC observations over the Indian equatorial and low latitude sectors

The ionospheric response during three distinct geomagnetic storms occurred in the year 2016 is investigated using GPS-TEC observations in the Indian equatorial and low latitude sectors. The three geomagnetic storms are considered for this study which were occurred on 20 January 2016 (2230 LT), 6 March 2016 (0230 LT) and 13 October 2016 (0530 LT) with minimum Sym-H values of −95 nT, −110 nT and −114 nT respectively. These three geomagnetic storms are different from one another in the sustainment of main and recovery phases and are occurred at three different local times corresponding to the Indian longitudes. This study brings out the major differences of these three geomagnetic storms characteristics and their distinct effects on the equatorial and low latitude ionosphere. Significant changes in the VTEC during main and recovery phases of these three storms are found to be mainly associated with prompt penetration electric fields and thermospheric neutral compositional changes. During the storm of 20 January 2016, positive storm effects during main and recovery phases of the storm are in association with the penetration electric fields. The complete main phase for the 6 March 2016 geomagnetic storm was occurred during night time and no changes in VTEC has been identified, which could be due to the weak background electron density. A positive storm effect is noticed during the recovery phases of the storms of 6 March 2016 and 13 October 2016, due to the storm induced electric fields differences and in particular due to the enhanced [O]/[N2] ratio in thermospheric composition. A strong positive storm effect caused by Co-rotating Interacting Region (CIR) induced disturbances after the 13 October 2016 storm is also discussed.

Lissa, D.; Venkatesh, K.; Prasad, D.; Niranjan, K.;

Published by: Advances in Space Research      Published on: aug

YEAR: 2022     DOI: 10.1016/j.asr.2022.05.027

Disturbance Dynamo; Geomagnetic storms; Positive Storm Effect; Prompt Penetration Electric Fields (PPEF); Total electron content (TEC)

The impact of a stealth CME on the Martian topside ionosphere

Solar cycle 24 is one of the weakest solar cycles recorded, but surprisingly the declining phase of it had a slow coronal mass ejection (CME) that evolved without any low coronal

Thampi, Smitha; Krishnaprasad, C; Nampoothiri, Govind; Pant, Tarun;

Published by: Monthly Notices of the Royal Astronomical Society      Published on:

YEAR: 2021     DOI: 10.1093/mnras/stab494

Ionospheric response to the 26 August 2018 geomagnetic storm using GPS-TEC observations along 80 E and 120 E longitudes in the Asian sector

Lissa, D; Srinivasu, VKD; Prasad, DSVVD; Niranjan, K;

Published by: Advances in Space Research      Published on:

YEAR: 2020     DOI:

L-band scintillation and TEC variations on St. Patrick’s Day storm of 17 March 2015 over Indian longitudes using GPS and GLONASS observations

The aim of the present study is to investigate the response of ionospheric total electron content (TEC), Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) scintillations during 17 March 2015 St. Patrick\textquoterights Day geomagnetic storm over Visakhapatnam, which is popularly known as Waltair (WALT) in the literature. GPS TEC observations obtained from five IGS stations (SGOC, IISC, HYDE, LCK4 and LHAZ) and WALT during the storm have been compared. The TEC derived from GPS, GLONASS constellations and CODE global ionosphere TEC map (GIM) over WALT has also been compared. Positive storm effect during the main phase of the storm and negative storm effect during the recovery phase of the storm were observed over the said stations. The variation of northern equatorial ionisation anomaly TEC (CODE GIM TEC maps) in response to the St. Patrick\textquoterights Day storm over four Indian longitudes (75oE, 80oE, 85oE and 90oE) has also been presented. Strong amplitude and phase scintillations were observed in the L-band signals of GPS and GLONASS constellations over WALT. Twelve satellite (Pseudo Random Noise) PRNs of GPS L1 and nine PRNs of each GLONASS L1 and L2-band signals were affected by strong amplitude and phase scintillation. The peak amplitude scintillation index (S4) obtained from the effected PRNs of GPS L1 signal and GLONASS L1-band signals over WALT range from 0.36 to 0.74 and 0.36 to 0.76, respectively. Strong fluctuations in rate of TEC index are noted over the said stations. This enhanced scintillation activity is mainly due to the main phase of the storm falls in the evening sector over the Indian region.

Srinivasu, K; Prasad, D; Niranjan, K; Seemala, Gopi; Venkatesh, K;

Published by: Journal of Earth System Science      Published on: 03/2019

YEAR: 2019     DOI: 10.1007/s12040-019-1097-6

Detection of ionospheric anomalies during intense space weather over a low-latitude GNSS station

The operational availability of Global Navigation Satellite System is affected by large-scale irregularities of the ionosphere. The space weather events induce several intense irregularities and cause the non-linear distribution of ionospheric electron density. Monitoring of ionospheric responses due to extreme space weather events plays a key role in trans-ionospheric radio wave propagation. In the present analysis, a novel technique based on wavelet transform has been implemented for the analysis and detection of ionospheric anomalies during two intense space weather events that occurred in 2013. The investigations have been carried out using the ionospheric observable, Total Electron Content (TEC), derived from the Global Positioning System (GPS) receiver located at an Equatorial Ionisation Anomaly region, KL University, Guntur, India (Geographic Lat.16.37\textdegreeN, Geographic Long. 80.37\textdegreeE). The effects of geomagnetic storms (Sym-H\ <=\ -100\ nT) on the perturbations of ionospheric TEC have been investigated. The algorithm of Continuous wavelet transform has been used to study and characterise the presence of ionospheric anomalies in the local time-scale plane. It can detect spatial and temporal details of ionospheric anomaly intensity during strong solar-terrestrial and geophysical events. It is observed that during the main phase of the geomagnetic storm that occurred during 17 March 2013, TEC enhanced by 7 TECU, while a suppression of 10 TECU in the GPS-TEC can be noticed during the main phase of the 29 June 2013 storm. The variation in the intensity of ionospheric TEC anomalies during storm time has been detected and compared to the intensity of the space weather events measured through solar and geomagnetic indices (F10.7, Sym-H, IMF Bz and IEF Ey).

Sivavaraprasad, G.; Ratnam, Venkata; Padmaja, Sree; Sharvani, V.; Saiteja, G.; Mounika, Y.; Harsha, Babu;

Published by: Acta Geodaetica et Geophysica      Published on: 12/2017

YEAR: 2017     DOI: 10.1007/s40328-016-0190-4

The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event

Some of the most intense solar flares measured in 0.1 to 0.8 nm x-rays in recent history occurred near the end of 2003. The Nov 4 event is the largest in the NOAA records (X28) and the Oct 28 flare was the fourth most intense (X17). The Oct 29 flare was class X7. These flares are compared and contrasted to the July 14, 2000 Bastille Day (X10) event using the SOHO SEM 26.0 to 34.0 nm EUV and TIMED SEE 0.1\textendash194 nm data. High time resolution, \~30s ground-base GPS data and the GUVI FUV dayglow data are used to examine the flare-ionosphere relationship. In the 26.0 to 34.0 nm wavelength range, the Oct 28 flare is found to have a peak intensity greater than twice that of the Nov 4 flare, indicating strong spectral variability from flare-to-flare. Solar absorption of the EUV portion of the Nov 4 limb event is a possible cause. The dayside ionosphere responds dramatically (\~2.5 min 1/e rise time) to the x-ray and EUV input by an abrupt increase in total electron content (TEC). The Oct 28 TEC ionospheric peak enhancement at the subsolar point is \~25 TECU (25 \texttimes 10¹² electrons/cm²) or 30\% above background. In comparison, the Nov 4, Oct 29 and the Bastille Day events have \~5\textendash7 TECU peak enhancements above background. The Oct 28 TEC enhancement lasts \~3 hrs, far longer than the flare duration. This latter ionospheric feature is consistent with increased electron production in the middle altitude ionosphere, where recombination rates are low. It is the EUV portion of the flare spectrum that is responsible for photoionization of this region. Further modeling will be necessary to fully understand the detailed physics and chemistry of flare-ionosphere coupling.

Tsurutani, B.; Judge, D.; Guarnieri, F.; Gangopadhyay, P.; Jones, A.; Nuttall, J.; Zambon, G.A.; Didkovsky, L.; Mannucci, A.J.; Iijima, B.; Meier, R.; Immel, T.J.; Woods, T.; Prasad, S.; Floyd, L.; Huba, J.; Solomon, S.; Straus, P.; Viereck, R.;

Published by: Geophysical Research Letters      Published on: 02/2005

YEAR: 2005     DOI: 10.1029/2004GL021475