A Simulation Study on the Latitudinal Variations of Ionospheric Zonal Electric Fields Under Geomagnetically Quiet Conditions

摘要

The influence of zonal electric fields as well as E × B plasma drifts on the ionosphere has been widely investigated, but the latitudinal variations of zonal electric fields have not been well understood. In this study, we investigate the driving mechanisms responsible for the latitudinal variations of zonal electric fields under geomagnetically quiet conditions using the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). A series of case-controlled TIEGCM simulations were conducted to explore the effects of neutral wind and ionospheric conductivity on the latitudinal variations of zonal electric fields. The major results are given as follows: (1) The eastward electric field at noon increases with latitude, which is mainly associated with latitudinal changes of poleward neutral winds. (2) The prominent latitudinal variations of zonal electric fields at sunrise and sunset are attributed to the strong longitudinal gradients of zonal winds, that is, the curl-free mechanism. (3) The changes of the zonal electric fields at a given location are affected by the dynamo effect globally, which also produces the latitudinal structure of zonal electric fields.