The Study Of Chorus Waves Excitation Associated With Enhancement Of Solar Wind Dynamic Pressure And The Statistical Of Electron Pitch Angle Distributions

We divided the dissertation into two parts,and we study,respectively,the response of the chorus waves with the solar wind dynamic pressure enhancement and the statistical of the electron pitch angle distributions(PADs)types in the magnetopause(8-12 Re).In the first part,by analyzing data from the magnetosphere particles observation MMS mission and OMNI database,we report an event of dayside chorus waves response to the solar wind dynamic pressure variations in the high L region,we present the fitting of electron phase space density and the results indicate that the anisotropy of electron temperature increases is related to the enhancement of solar wind dynamic pressure,and the electron flux with energy(16.06 keV to 27.53 keV)is obviously enhanced.We calculated the chorus waves growth rate by linear theory and found that during the solar wind dynamic pressure enhancement,the linear growth rate of the chorus waves increases,on the other hand,it is also found that the frequencies of the chorus waves would shift upward during solar wind dynamic pressure enhancement,and the frequency band of the chorus waves has been further widened,which has been verified the enhanced of solar wind dynamic pressure on the excitation of the chorus waves and the frequencies shift upward play an important role.In the second part,we use the MMS mission and OMNI database and statistically investigate the electron pitch angle distributions in the magnetopause,the paper selects the electron pitch angle differential flux data of two energy channels ME(200 eV-2 keV)and HE(2 keV-30 keV)observed by the MMS1 mission from September 2015 to December 2018,the statistical area extends a wider spatial region than previous studies.According to the statistical method in this paper,the six different pitch angle distributions types are judged by the ratio of the fluxes with different pitch angle,and introduced the ? index,the mian conclusion:(1)The pancake PADs mainly located in the lower L shells,and its occurrence rate obviously decreases with the increase of L shells.(2)The flat-top PADs occur in both the prenoon and afternoon side,its occurrence rate is nearly same in different MLT.(3)The occurrence rate of butterfly PADs is low,which is mainly distributed in the lower L shells and afternoon side.(4)The occurrence rates of cigar,isotropy,and rolling-pin PADs are very little for the electron with HE energy channels,nevertheless,those PADs occurrence rates relatively large for the electron with ME energy channels.The cigar PADs generally occur in the dawn and dusk sides,the global distribution of isotropy PADs looks alike similar with that of flat-top PADs,the rolling-pin PADs.(5)As the enhancement of solar wind dynamic pressure,the occurrence rate of pancake PADs decrease,on the contrary,the occurrence rate of butterfly PADs increase,but for HE energy channels,the occurrence rate of pancake PADs increase,and the occurrence rate of butterfly PADs decrease with the enhancement of solar wind dynamic pressure while L<12.