HR: 09:45h
AN: SM41B-08    [Abstracts]
TI: Magnetospheric responses to periodic variations in the solar wind dynamic pressure
AU: * Fujita, S
EM: sfujita@mc-jma.go.jp
AF: Meteorological College and JST, Asahi 7-4-81, Kashiwa, 277-0852, Japan
AU: Motoba, T
EM: motoba@stelab.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: Tanaka, T
EM: tatanaka@geo.kyushu-u.ac.jp
AF: Department of Geophysics and Planetary Sciences, Kyushu University and JST, Hakozaki, Higashi-ku, Fujuoka, 812-8581, Japan
AB: Before we investigate magnetospheric responses to various solar wind changes including IMF and dynamic pressure, it is essential to understand fundamental properties of the magnetospheric responses for simple solar wind variations. For this purpose, a global MHD model is a unique and powerful tool because we can assign any solar wind variations in the model [e.g., Tanaka, 1995]. In the present study, we investigate the magnetospheric response to periodic variations in the solar wind dynamic pressure with various time scales. Through the simulation. we obtain the following results. EThe magnetosheath is a buffer of the magnetosphere against short-period solar wind dynamic pressure variations. EThe shorter-period variations, the MHD-wave process is dominant in the magnetosphere. On the other hand, for the longer-period one, the magnetospheric process is associated with slowly varying convection system in the magnetosphere-ionosphere system. The criterion between the shorter and longer period is about 5 minutes. EFor shorter-period variations, spectral characteristics of the ground magnetic variations reflect those of the solar wind variation. Note that the field line resonances must be superposed on these spectral characteristics. EFor longer-period variations, the spectral characteristics of the ground magnetic variations are different from those of the solar wind variations. The ground magnetic variations have higher-harmonic spectral components of the original one of the solar wind variations. This is independent of the field line resonance mechanism.
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 2774 Radiation belts
DE: 2778 Ring current
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting