Interaction between direct penetration and disturbance dynamo electric fields in the storm‐time equatorial ionosphere

Abstract

The direct penetration of the high‐latitude electric field to lower latitudes, and the disturbance dynamo, both play a significant role in restructuring the storm‐time equatorial ionosphere and thermosphere. Although the fundamental mechanisms generating each component of the disturbance electric field are well understood, it is difficult to identify the contribution from each source in a particular observation. In order to investigate the relative contributions of the two processes, their interactions, and their impact on the equatorial ionosphere and thermosphere, the response to the March 31, 2001, storm has been modeled using the Rice Convection Model (RCM) and the Coupled Thermosphere‐Ionosphere‐Plasmasphere‐Electrodynamics (CTIPe) model. The mid‐ and low‐latitude electric fields from RCM have been imposed as a driver of CTIPe, in addition to the high latitude magnetospheric sources of ion convection and auroral precipitation. The high latitude sources force the global storm‐time wind fields, which act as the driver of the disturbance dynamo electric fields. The magnitudes of the two sources of storm‐time equatorial electric field are compared for the March 2001 storm period. During daytime, and at the early stage of the storm, the penetration electric field is dominant; while at night, the penetration and disturbance dynamo effects are comparable. Both sources are sufficient to cause significant restructuring of the low latitude ionosphere. Our results also demonstrate that the mid‐ and low‐latitude conductivity and neutral wind changes initiated by the direct penetration electric field preferentially at night are sufficient to alter the subsequent development of the disturbance dynamo.