Polar and Equatorial Ionospheric Electrodynamical Coupling Under a Prolonged Northward B<inf>z</inf> Interval

Abstract

The interplanetary magnetic field (IMF) significantly influences the global ionospheric electrodynamics, but it is still largely unknown the high- and low-latitude ionospheric electrodynamical coupling under long-duration northward IMF Bz (NBz) and By conditions. During the long-duration NBz and duskward By conditions (Kp < 2, AE < 100 nT, SYM-H > −25 nT) on 20 August 2014, six pairs of magnetometer data showed that daytime equatorial electrojet (EEJ) underwent strong decreases (reach up to 90%) at wide longitudes. Thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) captured well the decrease and the control simulations revealed that both effects of the NBz and By significantly change the plasma convection, Joule heating, and thermospheric winds at high latitudes; and penetration electric field (PEF) due to the NBz plays an important role in the decrease of the equatorial electric field. This study indicates the significant NBz effects on the equatorial ionospheric electrodynamics even during weak geomagnetic conditions, apart from the widely believed meteorological effects. Further study should be taken to disclose the relative contribution between geomagnetic and meteorological effects on the decrease of the equatorial electric field.