Geospace magnetic field response to the large and fast solar wind dynamic pressure change

摘要

We analyze the geospace magnetic field responses to the large and sharp solar wind dynamic pressure disturbances comparatively, including interplanetary shocks, simple solar wind dynamic pressure increase (not IP shock) and decrease events. The geosynchronons magnetic field shows strong positive response to the dynamic pressure change near the noon meridian, and weak response in the night-side of magnetosphere. However negative response is often observed in the midnight region. According our study, the geomagnetic indices SYM-H shows the distinct positive response to the change of solar wind dynamic pressure. The amplitude of the geosynchronous magnetic field response dBz could be determined by the change of the square root of the solar wind dynamic pressure near the noon meridian with high correlation as same as the geomagnetic indices SYM-H. The dBz at geosynchronous orbit near local noon and the amplitude of sudden impulses dSYM-H on the ground are highly correlated under the effect of IP shock or simple solar wind dynamic pressure increase event, differentiating from the dynamic pressure decrease event distinctly. It is shown that IP shock has some commonness with simple solar wind dynamic pressure increase event in affecting the geospace magnetic field.