Excitation Characteristics Of Whistler Waves And Acceleration Mechanism Of Cold Ions In Magnetic Reconnection

Magnetic reconnection is a fundamental and critical physical process that occurs in plasmas during space,astrophysical systems,and laboratory experiments.It refers to the process by magnetic field lines “break” and “reconnect”,resulting in changing the topology of magnetic field in the plasma,and converting magnetic energy into thermal and kinetic energy of the plasmas.Magnetic reconnection is a significant mechanism for coronal mass ejections and formation,and it plays a pivotal role in processes such as coronal heating and the input of plasma energy into the magnetosphere.Magnetic reconnection typically involves the conversion and release of magnetic energy,the generation of plasma waves,as well as particles acceleration.Plasma wave is a vital outcome of magnetic reconnection,which can effectively heats ions and electrons,dissipates particle energy,and generates anomalous resistivity,all of which can influence magnetic reconnection.Satellite observations demonstrate that there are various wave phenomena in the magnetic reconnection region,including plasma wave predominantly located near separatrix and in the outflow region.Whistler wave is a significant type of plasma wave that can accelerate and scatter electrons,transfer energy,and provide diagnostic information for the dynamics of magnetic reconnection.When the Earth’s magnetic field is active,the cold plasma in the plasma layer located in the low latitude area of the Earth is affected by the convection electric field,and flows out from the Earth’s magnetosphere to space,participating in the reconnection process near the sunside magnetopause and magnetotail in the form of a tongue-like plume.The cold plasma plume consists of ions and electrons with energies generally below 100 e V and is characterized by low velocity and high density.Cold plasma plumes affect ionospheric instability and plasma dynamics on the magnetosphere of the Earth,which have important effects on satellite communication,navigation and other technologies.The study of cold plasma plumes in Earth’s magnetosphere is of great significance for understanding the physical processes of Earth’s magnetosphere and the changes of space environment.It can also provide reference and enlightenment for future space technology and application.In recent years,different experimental and numerical simulation methods have been used to explore plasma fluctuations in magnetic field reconnection.Based on this,we use a 2.5D PIC(Particle-in-Cell)method to simulate the excitation characteristics of electron cyclotron whistler wave and left-polarized ion cyclotron whistler wave(L wave)in magnetic reconnection process.The simulation results show that quasi-parallel and anti-parallel whistler waves can be excited in the separation line region and the outflow region respectively.In addition,we analyze the interaction between electron cyclotron whistler waves and electrons via WPIA(Wave-Particle Interaction Analyzer)method.The results show that electron cyclotron whistler waves play an important role in energy release and conversion,because during magnetic reconnection,electrons with small mass can move rapidly under magnetic field perturbations.At the same time,we investigate the excitation mechanism of electron cyclotron whistler wave and ion cyclotron whistler wave by numerical simulation.In addition,we compare the case where there is no cold plasma flow(case 0)with the case where cold plasma flow loaded at two local locations(case 1 and case 2).In case 1,the loading position of the cold plasma flow is along the inflow direction,pointing to the reconnection point(X point).In case 2,the loading position of the cold plasma flow is parallel to the inflow direction and points to the outflow region.We investigate the acceleration and heating of cold ions near the upper separation line region in case1 and case 2.Due to the weak magnetic field,the cold ions in the diffusion region are subjected to E × B,which increases the cyclotron radius of the cold ions and makes them enter the outflow region.As the Hall field at the separatrix line of dissipation region is negative,cold ions are prevented by the Hall field and cannot cross the upper separatrix line region.In case 1,cold ions are accelerated in the negative z direction at the upper part of the inflow region by the nonideal electric field(E + vci × B)z.During this process,the cold ions undergo demagnetization drift due to the limited Larmor radius effect.The effect of cold ions on the reconnection rate is also discussed.The results show that the reconnection rate decreases when cold ions enter the diffusion region.However,there was no significant change in the reconnection rate in case 2.