Massive Multi-Mission Statistical Study and Analytical Modeling of the Earth's Magnetopause: 2. Shape and Location

摘要

The Earth magnetopause is the boundary between the magnetosphere and the shocked solar wind. Its location and shape are primarily determined by the properties of the solar wind and interplanetary magnetic field (IMF) but the nature of the control parameters and to what extent they impact the stand-off distance, the flaring, and the symmetries, on the dayside and night side, is still not well known. We present a large statistical study of the magnetopause location and shape based an extensive multi-mission magnetopause database, cumulating 17,230 crossings on 17 different spacecraft, from the dayside to lunar nightside distances. The results confirm the power-law dependency of the stand-off position on the solar wind pressure. The IMF clock angle itself (all amplitudes combined) does not impact the stand-off distance, nor does the cone angle. However, the magnetopause is found to move Earthward as the IMF gets stronger and more southward. All upstream conditions combined, it is found that the function used at the root of several analytical models still holds at lunar distances. We find that the equatorial flaring is larger than the meridional one. However, the meridional flaring is found to depend on the seasonal tilt conditions, being larger in the summer hemisphere. The flaring is also found to depend on the IMF clock angle. Meridional flaring increases as the IMF turns south and is then larger than the equatorial flaring. The equatorial flaring barely changes or weakly increases as the IMF turns northward, and is larger than the meridional flaring for northward conditions. The results of the study pave the way for the elaboration of a new analytical empirical expression of the magnetopause location and shape.