Variation on Solar Wind Parameters and Total Electron Content Over Middle- to Low-Latitude Regions During Intense Geomagnetic Storms

Streams of the particle ejected from the Sun and the extreme space weather conditions like storms, high-speed streamers (HSSs), interplanetary coronal mass ejections (ICMEs), corotating interaction regions (CIRs), and interplanetary shocks (IS) termed as geomagnetic storms have massive influence in the climate and components of the Earth's upper atmosphere such as total electron content (TEC). The study of TEC helps to understand variations in ionospheric electron density during geomagnetic storms. Global ionospheric maps of TEC are a real-time mapping of GPS observations produced by ground-based stations. In this paper, we have analyzed three intense geomagnetic storms of the year 2015: during 16-21 March 2015 (the St. Patrick's Day storm), 21-24 June 2015, and 18-22 December 2015. We present the variations of IMF-Bz, solar wind parameters (Vsw, Nsw, and Psw), and geomagnetic indices (AE and SYM-H) and the variations of vertical total electron content (VTEC) using simultaneous VTEC data from 12 GPS-TEC stations over the Indian, Australian, Brazilian, and South African regions. We describe contrast in TEC throughout the globe using global ionospheric maps at a regular 2 hr interval of UT during the three intense geomagnetic storms. Moreover, we observed that heavily TEC-influenced areas were found to be transposing through the equatorial plane starting from eastern sectors to the western sectors. The Indian Ocean, Atlantic Ocean, and South Pacific Ocean sectors were affected flowingly. Global ionospheric maps evince that Indian and Brazilian sectors were affected heavily explaining the traveling ionospheric disturbances (TID) and equatorial anomaly as seen in those areas. The equatorial and low-latitude regions have been mainly affected by geomagnetic storms. All these results suggested that the acute disruption of global winds (surging toward the equator from higher latitudes) and electric fields commenced from magnetosphere-ionosphere interaction causing the severe modification in the equatorial, low-latitude region. We also checked the cross correlation of VTEC of LCK3 station and various other stations during the period of high solar and geomagnetic activities; the correlation gradually increased with the nearby stations by latitudes in most of the cases which was another intriguing result. Thus, these results suggested that the storms were affected globally, which is why we believe that variation of TEC over various stations of the globe could turn out to be very helpful in predicting solar wind coupling with the magnetosphere-ionosphere.