Ionospheric variations during geomagnetic storms of 7–8 September, 2017

Two very intense solar flares of magnitudes X2.2 and X9.3 erupted on September 6, 2017 at 09:10 UT and 12:02 UT triggering large space weather modulations on earth. We analyze the ionospheric response to the geomagnetic storm event that occurred post the flares on 7–8 September 2017 on five selected stations in the northern (Lhasa, Lucknow, Dibrugarh, Quezon City) and southern hemisphere (Cocos). This storm occurred just after the X9.3 solar flare on 6
^th
September. The following figure represents the effect of the storm on Vertical Total Electron Content. It is seen that the VTEC increased significantly on 6-7 September in the northern hemisphere while TEC remained nearly uniform in the southern hemisphere. The TEC decreased on 8–10 September in the NH while in the SH, TEC decreased on 9
^th
and then increased on 10
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onwards. There is a sudden risein the average VTEC on 11th September more than pre flare levels in all stations. Ionograms obtained over Cocos showed that for the solar flare day E layer disappears whereas, for geomagnetic storm days sporadic E is observed. The inter hemispheric asymmetric variation in TEC and E layer activities over Cocos are further examined using electron density profiles, maximum electron concentration (NmF2) and data from COSMIC, GRACE and SWARM satellites. The results from this comprehensive analysis will be presented.