Ionospheric response to Strong Geomagnetic Storms during 2000-2005: An IMF clock angle perspective

TL;DR

This study analyzes how strong geomagnetic storms from 2000-2005 affect the equatorial ionosphere, highlighting the critical role of IMF clock angle and By component in prompt ionospheric irregularities.

Contribution

It demonstrates that equatorial irregularities typically occur within 3 hours of IMF clock angle transition, refining previous understanding of timing for storm-induced ionospheric responses.

Findings

91% of cases show irregularities within 3 hours of IMF transition

IMF By significantly influences prompt penetration of electric fields

Improves timing window from 4 hours to 3 hours for irregularity onset

Abstract

This paper presents the equatorial ionospheric response to eleven strong-to-severe geomagnetic storms that occurred during the period 2000-2005, the declining phase of the solar cycle 23. The analysis has been performed using the global ion density plots of Defense Meteorological Satellite Program (DMSP). Observations show that for about 91% of the cases, post-sunset equatorial irregularities occurred within 3h from the time of northward to southward transition of the Interplanetary Magnetic Field (IMF) clock angle, thus bringing out the importance of the role played by IMF By in the process of Prompt Penetration of Electric Field (PPEF) in addition to the IMF Bz. This is an improvement from the previously reported (Ray et al.,2015) 4h window of ESF generation from the southward IMF Bz crossing -10 nT.