Response Of Magnetospheric Cold Plasmas To Geomagnetic Storms,Substorms And EMIC Waves

Plasma,as the main composition of matter in the universe,is one of the important topics in space physics research.The plasmasphere is the coldest part of the magnetosphere,the plasma in plasmasphere co-rotated with the earth is constrained by the electromagnetic field of near-Earth space.The density distribution and dynamic changes of the plasma are affected by physical processes such as magnetic storms,substorms,and wave-particle interactions in the magnetosphere.The change in the plasma distribution will also affect the excitation of waves in the magnetosphere,which will indirectly affect the precipitation of high-energy particles.In this paper,the changes of the plasmasphere during magnetic storms and substorms are simulated and observed,and the effect of EMIC(Electromagnetic Ion Cyclotron)waves on the distribution of low-energy ions is discussed.The main results we get are as follows:1.We use the proton phase-space distribution based on the convective electric field driven by the AL index to buid a new model of plasmasphere to study the evolution of the plasmasphere during continuous magnetic storms.We simulated the evolution of the plasmasphere in the magnetic equatorial plane from February 18 to22,2014.Our method can simulate some meticulous evolutions of the plasmasphere during the magnetic storm from the view of the magnetic equatorial plane.The overall response of the plasmasphere to the magnetic storm is within 3 hours,but the impact of a large magnetic storm on the plasmasphere is long-term,which can reach 1-2 days.After the magnetic storm,the plasmasphere is eroded,it takes a certain time to refill the plasmasphere.During this period,if a magnetic storm occurs again,the plasmasphere will continue to be eroded and shrink.This shows that refilling process takes longer than erosion.2.Analysis the configuration and evolution of the plasmasphere from the moon's view.(1)We use a simple empirical formula of electron density based on IMAGE/RPI(Imager for Magnetopause-to-Aurora Global Exploration / radio plasma imager)model to image the plasmasphere at the moon's perspective.The imaging method can basically reflect the side shape of the plasmasphere.The inclination of the geomagnetic field has a great impact on plasmasphere simulation.(2)Using the extreme ultraviolet data of the Chang'e-3 lander,We analyzed the configuration of the plasmasphere under different geomagnetic conditions.We found that during the quiet period,the plasmasphere was diffused and boundary of the plasmaspause is clearunder active period.In addition,the morphology of the plasmasphere in side view under different geomagnetic conditions is effected by the magnetic field configuration.(3)On February 21,2014,the observation of the plasmasphere under the condition of substorm and steady magnetospheric convection(SMC)was analyzed.In this observation,the actual filling rate of the plasmasphere is faster than the result we simulated.Because the SMC has an initial substorm,a total of two substorms occurred in this process.We found that after the SMC began,the plasmasphere did not continue to shrink,and the boundary gradually diffused.(4)We observed two contractions of plasmapause on the dayside.Combined with the RBSP(Radiation Belt Storm Probes)data and the simulation in Chapter 3,we believe that the plume structure at 15 MLT around will affect the boundary of the plasmasphere from side view3.Discuss the theoretical basis of EMIC waves modulation on ion pitch angle distribution(IPD)and get simulation results.The wave field of the EMIC waves is solved by the linear Hall-MHD(Hall-Magnetohydrodynamics)theory,and the influence of the EMIC waves on IPD in theory is also studied.We obtained the dispersion relationship of the EMIC waves and the evolution of them from the preliminary simulation.In subsequent simulations,we found that large-amplitude EMIC waves significantly modulate the IPD in low-energy band,affected by the bulk velocity triggered by large-amplitude EMIC waves,the number density will enhance around PA? 90,beyond that,the ion pitch angle will be modulated by the EMICwaves,the modulation period is half of the EMIC waves' period.The modulation is obvious for cold ions,and there is almost no modulation characteristic for hot protons.is more concentrated around PA?90 compared with,the PA distributionand the modulation period of are significantly different from and ions.In addition,the modulation will become more obvious as the amplitude increases.The period of pitch angle modulation will be modulated when the wave normal angle 0,this is caused by the superposition of high-frequency harmonic waves generatedby the wave-wave coupling.