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.

Response of the equatorial ionosphere at dusk to penetration electric fields during intense magnetic storms

“…We plan to use this framework to develop algorithms for operational systems support for AFRL's global Scintillation Network Decision Aid system [Groves et al, 1997]. It is hoped that these significant findings will also be incorporated in global magnetosphere-ionosphere-thermosphere coupled models currently under development [Maruyama et al, 2005;Huba et al, 2005;Lin et al, 2005].…”

“…The dynamic and electrodynamic responses at low latitudes have been investigated by Fuller-Rowell et al [2002] by using a coupled three-dimensional model of the thermosphere, ionosphere, plasmasphere, and electrodynamics. Modeling the disturbance dynamo phase is complicated because the disturbance dynamo electric fields have to operate on an ionosphere that has been modified by the initial prompt penetration electric fields [Maruyama et al, 2005]. Our understanding of this complex interaction can be advanced by global ionospheric modeling of many storms and model validation with observations at globally dispersed locations [Fejer et al, 1990;Greenspan et al, 1991;Fejer and Scherliess, 1995;Fejer and Emmert, 2003;Basu et al, 2001aBasu et al, , 2001bBasu et al, , 2005aBasu et al, , 2005bMartinis et al, 2005].…”

Simulation study of penetration electric field effects on the low‐ to mid‐latitude ionosphere

“…However, determination of the impact of penetration electric fields on the ionosphere based on a selfconsistent electrodynamic model has been lacking [Huba et al, 2003;Maruyama et al, 2005].…”

“…In addition, the 'fountain effect' is enhanced in the postsunset period. Citation: Huba, J. D., G. Joyce, S. Sazykin, R. Wolf, and R. Spiro (2005), Simulation study of penetration electric field effects on the low-to mid-latitude ionosphere, …”

Effects of long-lasting interplanetary magnetic field perturbations on the equatorial ionosphere

“…However, we can partially see agreement between them, e.g., ~15 LT on July 3 and ~03 LT on July 7. The calculated velocity would be modified due to other factors such as coupling effects between PPEF and DDEF (Maruyama et al, 2005), occurrence of substorm-like disturbance. Indeed, there exist injection events in the magnetotail during the HILDCAA period (not shown here).…”