Equatorial Electrojet (EEJ) Response to Interplanetary (IP) Shocks

Abstract

Interplanetary (IP) shocks are known to cause significant modifications in Earth's magnetospheric and ionospheric current systems. The sudden enhancement of solar wind dynamic pressure (P_Dyn) associated with IP shocks could induce convection electric fields at high-latitude ionosphere which can promptly penetrate to equatorial and low-latitude regions. Additionally, prompt penetration electric field disturbances may also be induced due to the sudden southward/northward turnings of the Interplanetary Magnetic Field (IMF B_Z) (eastward/westward turnings of the interplanetary electric field, IEF_y) during IP shocks. The resultant electric field disturbances can significantly alter the ionospheric electrodynamics and equatorial electrojet (EEJ). In this study, the EEJ response to a large number of IP shocks that occurred during 2001–2021 has been investigated. The magnitude of the EEJ response to IP shocks shows a clear local time dependence and varies linearly with the change in solar wind dynamic pressure. The EEJ response is also found to depend considerably on the solar activity (F10.7 solar flux) and the polarity changes in IMF B_Z associated with IP shocks. For the first time, an empirical relation is derived that can quantitatively estimate the EEJ response to IP shocks using a large number (306) of events that occurred over a span of two solar cycles. The derived empirical relation is found to be very accurate in predicting the response of the EEJ and exhibits an excellent correlation with observations.