The Study Of Formation And Evolution Of Plasmoids And Flux Rope Structures In Earth's Magnetosphere

At the dayside magnetopause, the transient magnetic reconnection can lead to the formation of flux rope structures connecting interplanetary and magnetospheric field lines. Such structures might become the vital channels for the transfer of mass, energy, and momentum from the solar wind to the magnetosphere. In the course of substorms, the energy stored in the magnetotail is gradually dissipated by ejecting single or multiple plasmoids. The energy released by the plasmoids and associated tailward fast flow was estimated to be roughly 10¹⁵J, which is the same order as the energy released to the auroral ionosphere in a substorm. In recent years, the observation data detected by ISEE, Geotail, IMP-8 and Cluster II were analyzed, and many papers about the theoretical models and numerical simulations of the flux rope structures at the dayside magnetopause and plasmoid-like structures in the magnetotail were presented. The formation and evolution of plasmoids and flux rope structures in Earth's magnetosphere has become an important subject in magneospheric physics.After a review of the observation and research status on the plasmoids in the magnetotail and the flux rope structures at the dayside magnetopause, the 2.5D MHD simulations to study the reconnection processes occured in the magnetotail and magnetopause are carried out in this thesis. On the basis of the simulations, we investigated the occurrence of various magnetic structures in the magnetotail and the formation and evolution of the flux rope structure with a twisted topology at the dayside magnetopause in terms of magnetic helicity.As well known, the cross-tail component B_y in the magnetotail is directly proportional to the interplanetary magnetic field (IMF) B_y component, and its variation is significant during a substorm. The 2.5D MHD study indicates that the occurrence of...