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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, A12210, doi:10.1029/2007JA012664, 2007

Response of the magnetic field in the geosynchronous orbit to solar wind dynamic pressure pulses

C. Wang

State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China


J. B. Liu

State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China
Graduate School of Chinese Academy of Sciences, Beijing, China


Z. H. Huang

State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China


J. D. Richardson

Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA


Abstract

We do a statistical survey of solar wind dynamic pressure (P d ) pulses and geosynchronous magnetic fields observed between 1998 and 2005. In geomagnetic quiet times with Dst > −50 nT, we find 111 solar wind dynamic pressure pulses which produce geosynchronous magnetic field responses. These responses are often observed by two or three GOES spacecraft at different local times in geosynchronous orbit. The magnitudes of the geosynchronous magnetic field changes (dB z ) have a peak near the noon meridian, similar to the results obtained in the study of the response of the geosynchronous field to the large and sharp solar wind dynamic pressure variations. However, the relative change of the geosynchronous magnetic field dB z /AV-B z (where AV-B z is the average of the geosynchronous magnetic field B z observed during the response to the pressure pulse) depends weakly on the local time; thus the change of B z (dB z ) is proportional to the average field (AV-B z ). As the magnitude of the relative change of solar wind dynamic pressure (dP d /P d ) increases, the rate of geosynchronous magnetic field variation increases correspondingly. These results imply that the magnitude of the geosynchronous magnetic field response could be determined by AV-B z . In addition, the interplanetary field orientation does not affect the response significantly. Using an MHD code which models the global behavior of the solar wind-magnetosphere-ionosphere system, we reproduce the main characteristics of the observations.

Received 23 July 2007; accepted 20 September 2007; published 19 December 2007.

Keywords: Solar wind dynamic pressure; geosynchronous field.

Index Terms: 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2753 Magnetospheric Physics: Numerical modeling; 2164 Interplanetary Physics: Solar wind plasma; 2169 Interplanetary Physics: Solar wind sources.

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Citation: Wang, C., J. B. Liu, Z. H. Huang, and J. D. Richardson (2007), Response of the magnetic field in the geosynchronous orbit to solar wind dynamic pressure pulses, J. Geophys. Res., 112, A12210, doi:10.1029/2007JA012664.