Study Of The Magnetopause Location And Shape Under Extreme Interplanetary Conditions

When extreme interplanetary conditions occur, the magnetopause moves inside geosynchronous orbit, and then spacecraft, aviation, communication, navigation and Electric power grid would be damaged. So the magnetopause location research is very important on space weather forecast and space environmental monitoring.The location and shape of the magnetopause has been studied by many researchers for more than four decades. The studies have proved that Solar wind dynamic pressure Dp and Interplanetary magnetic field IMF Bz are two main factors to affect the magnetopause location and shape, and many magnetopause empirical models are developed by using magnetopause crossing data. However, the satellite magnetopause crossing data used in the previous empirical models are lack of points under extreme interplanetary conditions or on the region of high-latitude and XGSM<-10Re. Because of the limitations of satellite magnetopause crossing data, we use the 3D MHD simulation to study the location and shape of magnetopause under extreme interplanetary condition.We discuss the effects of solar wind speed and density on dayside reconnection power, and collect the upstream solar wind conditions of big storms from 1997 to 2007. According to statistical result, we calculate 72 cases with extreme interplanetary conditions. The magnetopause location is identified by the method of flow in this paper. Through the analysis of the magnetopause location data, a new dynamic 3D asymmetric magnetopause model is developed. This model is parameterized by Dp and IMF BZ. The coefficients are fitted by the Levenberg-Marquart method.On the basis of this model under extreme interplanetary conditions, the subsolar point decreases with increasing Dp and increasing Dp causes the decrease of the magnetopause size but almost keeps the magnetopause shapes self-similar; with increasing southward IMF BZ, the subsolar point decreases slightly, the level of tail flaring decreases and magnetopause indentation center moves towards low-latitude. The analysis of simulation data about the solar storms on August 1,2010 and on September 1,1859 shows that:compared with Shue et al. [1998] model and Lin et al. [2010b] model, the new magnetopause model is better to describe the global magnetopause under extreme interplanetary conditions.