Study Of The Size And Shape Of The Magnetopause: Based On The Global MHD Simulation For The Earth's Magnetosphere

There are few models for the high-latitude magnetopause because of the limit of the satellite observations data. This paper studies the relationship between the location and shape of the magnetopause in the equatorial plane and the noon-midnight meridian plane and the solar wind parameters (the interplanetary magnetic field B_z and the dynamic pressure D_p). And we also present a predictive model for each of them. Maximum of the magnetopause current intensity was used to identify the magnetopause at these locations in this paper. The function which was presented by Shue et al. in 1997 based on the satellite observational data can not only be applied to our simulation data in the equatorial plane but also to those in the noon-midnight meridian plane, in which the standoff distance r₀ and the flaring level of tailαcontrol the location and shape of the magnetopause.The dynamic pressure D_p and the z component of interplanetary magnetic field B_z are the main factors that control the location and shape of the magnetopause. We find that r₀ decreases with increasing D_p in the equatorial plane. r₀ and D_p are related by a power functional relation, but value of the power law is a little smaller than theoretical value and empirical value. r₀ decreases with increasing southward B_z when B_z is southward. For northward B_z , r₀ increases with increasing northward B_z .αchanges very little with the solar wind conditions, which means the magnetopause in the equatorial plane is strong self-similar.The location and shape of the magnetopause in the noon-midnight meridian plane prove to be more complicated than in the equatorial plane. Although the cusp is ignored, the simulation data should still be fitted by two different curves. For southward IMF B_z , r₀ decreases with IMF B_z increasing. For northward IMF B_z , r₀ increases with increasing northward B_z On the whole, r₀ increases when B_z turning northward from southward, and the influence of B_z on r₀ becomes weaker. r₀ is mainly affected by the dynamic pressure. r₀ decreases with D_p increasing. The other parameter of the functionαincreases with the south component of the IMF increasing, which means the magnetopause flares more strongly and more magnetic flux transfers from the dayside to the nightside. The value ofαis slightly larger for larger D_p, which implies that D_p also plays a role in flux transfer from the dayside to the nightside.