Equatorial Ionospheric Response to Super Geomagnetic Storm of May 10-11, 2024, over Indian Sector: Results from Ground and Space Based Observations

The equatorial ionospheric response to the super geomagnetic storm of May 10-11, 2024, over the Indian region is examined through ground-based and space-based observations. The storm was triggered by the interaction of the southward-oriented interplanetary magnetic field (IMF Bz) with the Earth’s northward magnetic field, leading to a rapid compression of the dayside magnetopause and a significant geomagnetic storm commencing at 16:00 UT. The SYM-H index dropped to -518 nT, resulting in substantial ionospheric disturbances globally, including India. Observations revealed a notable reduction in ionospheric density during the post-midnight hours on May 10-11. On May 11, a sharp rise in ionospheric height to approximately 850 km was recorded during the dawn sector, accompanied by an upward drift of about 130 m/s, attributed to an overshielding electric field from the northward turning of IMF Bz. Further analysis using ionosonde data, Equatorial Electrojet (EEJ) strength, GPS Total Electron Content (TEC), and COSMIC density profiles during the recovery phase showed significant density oscillations and suppression of the equatorial ionization anomaly (EIA). These effects were linked to multiple electric field penetrations and a westward disturbance dynamo electric field. The density reduction observed in the post-midnight sector is attributed to a westward penetration electric field pushing ionization to lower altitudes, thereby increasing recombination rates. Additionally, transequatorial meridional winds may have played a role in displacing ionization from the equator.