HR: 1340h
AN: SM43B-1325    [Abstracts]
TI: Revisiting the Bimodal Response of the Magnetosphere – Truth or Fiction
AU: * Bargatze, L F
EM: lfb@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Box 951567, Los Angeles, CA 90095-1567, United States
AB: The bimodal response model of the magnetosphere was proposed to explain how substorm current systems respond to solar wind coupling. The model is simple. It suggests that the magnetospheric system responds on two different time scales, to a motional electric field impulse imposed across magnetosphere the by the solar wind. The original work, published over 20 years ago, examined the linear impulse response of the auroral electrojet AE indices to the solar wind input parameter VBs calculated by using IMP-8 observations. The VBs-AL filters were found to exhibit two response peaks, one centered at an ~20-min time lag, the other at ~70-min. The two peaks were interpreted as the superimposed responses of the convection current system driven directly by dayside reconnection (the 20-min peak) and the substorm current wedge driven by the release of energy stored in the magnetotail following formation of an x-line in the near-Earth tail (70-min peak). The data set analyzed contained only ~73 days of data. This is small compared to the magnitude of data based compiled over the last decade from Wind and ACE. We have repeated the original study utilizing nearly 10 years of solar wind observations from ACE. The wealth of data allows one to study long-term variations in magnetospheric response, characterized by the AE indices and the polar cap PC index. Changes in response character with season also will be addressed.
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 2784 Solar wind/magnetosphere interactions
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting