Role of Impact Angle on Equatorial Electrojet (EEJ) Response to Interplanetary (IP) Shocks

Abstract

Interplanetary (IP) shocks are one of the dominant solar wind structures that can significantly impact the Geospace when impinge on the Earth's magnetosphere. IP shocks severely distort the magnetosphere and induce dramatic changes in the magnetospheric currents, often leading to large disturbances in the geomagnetic field. Sudden enhancements in the solar wind dynamic pressure (PDyn) during IP shocks cause enhanced high‐latitude convection electric fields which penetrate promptly to equatorial latitudes. In response, the equatorial electrojet (EEJ) current exhibits sharp changes of magnitudes primarily controlled by the change in PDyn and the local time. In this paper, we further investigated the influence of shock impact angle on the EEJ response to a large number (306) of IP shocks that occurred during 2001–2021. The results consistently show that the EEJ exhibits a heightened response to the shocks that head‐on impact the magnetosphere (frontal shocks) than those with inclined impact (inclined shocks). The greater EEJ response during the frontal shocks could be due to a more intensified high‐latitude convection electric field resulting from the symmetric compression of the magnetosphere. Finally, an existing empirical relation involving PDyn and local time is improved by including the effects of impact angle, which can quantitatively better predict the EEJ response to IP shocks.