HR: 17:30h
AN: SM52F-07    [PDF]
TI: The Magnetospheric Convection System in the Sudden Impulse
AU: * Fujita, S
EM: sfujita@mc-jma.ac.jp
AF: Meteorological College, Asahi 7-4-81, Kashiwa, 277-0852 Japan
AU: Tanaka, T
EM: tatanaka@geo.kyushu-u.ac.jp
AF: Department of Earth and Planetary Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-ku,, Fukuoka, 812-8581 Japan
AU: Kikuchi, T
EM: kikuchi@crl.go.jp
AF: Communications Research Laboratory, Nukui-Kita machi, Koganei, 184-8795 Japan
AB: We investigate numerically simulated disturbances of plasma convection in the magnetosphere-ionosphere system during a geomagnetic sudden commencement (SC) interval. The disturbance is excited by the solar wind density impulse impinging on the dayside magnetopause. Before the impulse arrives at the magnetopause, the magnetospheric convection essentially exhibits steady plasma shear motion that induces the field-aligned current. It is also noted that the magnetospheric current is the diamagnetic current that flows along the equi-contour lines of pressures. Divergence and convergence of the magnetospheric current is associated with the field-aligned current. It is noteworthy that the magnetospheric convection and current is connected self-consistently with the ionospheric convection and current through the field-aligned current in the stationary state. In the first stage of the SC, the compressional plasma disturbance is dominant in the dayside magnetosphere. On the other hand, the compressional disturbance does not arrive at the ionosphere because the ionospheric disturbance is essentially incompressible. This compressional disturbance appears in the first 3 - 4 min. of the SC interval. The ionospheric convection pattern is not corresponding to the magnetospheric convection pattern in this stage. After the compressional disturbance disappears, the magnetospheric convection flow exhibits a shear-like pattern. The ionospheric convection becomes consistent with the magnetospheric convection in the second stage. However, there appears a peculiar transient convection system in the nightside magnetosphere. This convection, driven by compression of the magnetospheric flank when the solar wind impulse is passing the flank, is moving to midnight magnetosphere. When the convection arrives at the midnight, it disappears. In the final stage of the SC when the transient convection disappears, a new steady convection in the magnetosphere-ionosphere system is established. This convection corresponds to the new condition of the solar wind after the impulse.
DE: 2708 Current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2753 Numerical modeling
DE: 2760 Plasma convection
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting