HR: 1340h
AN: SA33A-1053    [Abstracts]
TI: Stormtime Electric Fields at High-Equatorial Latitudes as Observed by the Magnetometers, Incoherent-Scatter Radar and Satellite
AU: * Kikuchi, T
EM: kikuchi@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furocho, Chikusaku, Nagoya, Aic 464-8601, Japan
AU: * Kikuchi, T
EM: kikuchi@stelab.nagoya-u.ac.jp
AF: National Institute of Information and Communications Technology, 4-2-1, Nukui-Kita, Koganei, Tok 184-8795, Japan
AU: Hashimoto, K K
EM: hashi@kiui.ac.jp
AF: Kibi International University, 8, Iga-machi, Takahashi, Oka 716-8509, Japan
AU: Shinbori, A
EM: shinbori@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furocho, Chikusaku, Nagoya, Aic 464-8601, Japan
AU: Fejer, B G
EM: bfejer@cc.usu.edu
AF: Center for Atmospheric and Space Science, Utah State University, 4405 Old Main Hill, Logan, UT 94322-4405, United States
AB: During the main phase of a geomagnetic storm, the convection electric field was significantly enhanced by strong southward IMF, and was transmitted to the polar ionosphere along geomagnetic field lines. The convection electric field penetrated into low latitude ionosphere, driving DP2 currents in the global ionosphere, composed of two-cell Hall current vortices at high latitude and Pedersen currents amplified by the Cowling effect at the dayside geomagnetic equator. The penetrated electric field was mapped into the ionospheric F-region and further into the inner magnetosphere. As a result, we observed upward motion of the ionosphere at low latitude on the dayside, and rapid development of the storm ring current. During the recovery phase of the storm, on the other hand, the electric field was reversed due to the overshielding effect, resulting in the equatorial counter-electrojet. It is shown that the overshielding occurred when the auroral oval shifted rapidly poleward. Both the equatorial DP2 currents and the counter-electrojet contributed to enhance the magnitude of the geomagnetic storm at the dayside geomagnetic equator, of which magnitude was 2.7 times that of the low latitude storm. The observational facts suggest that the convection electric field penetrated to low latitude may play a crucial role in development of the ring current, while the overshielding may reduce or reverse the electric field in the inner magnetosphere, ceasing the development of the ring current. It should be noted that another kind of reversed electric field often appears during the storm main phase, which might be caused by the disturbance dynamo. In this talk, we show several examples of these three kinds of stormtime electric fields in the global ionosphere and in the inner magnetosphere, using data from the magnetometer network, Jicamarca incoherent-scatter radar and AKEBONO satellite.
DE: 2409 Current systems (2721)
DE: 2411 Electric fields (2712)
DE: 2415 Equatorial ionosphere
DE: 2431 Ionosphere/magnetosphere interactions (2736)
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting