Observational Study On Magnetic Structure And Current System Of The Dayside Magnetopause For Open Magnetosphere

As the boundary layer between the solar wind and the magnetosphere,the magnetopause controls the transmission of mass,momentum and energy of the solar wind to the magnetosphere.When the interplantary magnetic field directs southward,magnetic reconnection occurs at the magnetopause,forming an open magnetopause.The formation of the open magnetopause means that plasma in the solar wind can be continuously transmitted to the earth through the magnetic field lines,which in turn affects the energy transformation of the Earth's magnetosphere and the change of the magnetic field topology.Therefore,it is of great significance to study the related physical phenomena of the open magnetopause.It can not only help for a more thorough understanding of the magnetic field structure and current distribution of the earth's magnetopause,but also lay a more solid theoretical foundation for the subsequent research on planetary magnetosphere physics.In this dissertation,we use data and the multiple-point measurements from MMS to analyse the structure of the rotational discontinuities associated with steady-state reconnection,and the evolution of the flux transfer events associated with transient reconnection.The formation of the rotational discontinuities opens a window for the earth's magnetosphere to directly contact the solar wind,whose plasma can then directly enter the magnetosphere.We find that the magnetic field has a minimum value at the center of the rotational discontinuities,in addition to satisfying some conventional ideas in classic textbook.The magnetic field gradient has a maximum value,which indicates that the topological structure of the magnetic field changes significently when the satellite passes through the rotational discontinuities.In addition,the current density also has a maximum,especially the field-aligned component of the current,which is also in line with the classical description of the current at the subsolar-point.It is well know that flux transfer events occur to form a flux tube across the magnetopause,connecting the magnetosphere to the magnetosheath.Based on the previous studies,we further studied the force-free configuration of the flux transfer events,and summarized the force-free characteristics.The control factors of the force-free configuration are forecasted,which will be useful in our futher study.