The Study Of Spatial Distribution Characteristics And Radiation Belt Electron Scattering Coefficient Of Chorus Waves In Jupiter’s Magnetosphere

Plasma waves can accelerate energetic particles in Jupiter’s magnetosphere,and chorus waves are regarded as an important acceleration mechanism contributing to the formation of relativistic and ultra-relativistic electrons in the Jovian radiation belts.The wave-particle interaction caused by chorus waves have an important contribution to the electron dynamics process of Jupiter’s radiation belt.Therefore,it is necessary to conduct correlation analysis and research on chorus waves in Jupiter’s magnetosphere.In this paper,we focuses on the study of spatial distribution characteristics and electron scattering effect of chorus waves in Jupiter’s magnetosphere.Firstly,we used the data of JUNO WAVES instrument to study the spatial distribution characteristics of chorus waves in Jupiter’s magnetosphere,then the parameter quantization of radiation belt electron scattering by chorus in the Jovian magnetosphere were carried out,finally we study the importance of electron distribution profiles to chorus wave driven evolution of Jovian radiation belt electrons.Conclusions are as follows:（1）Through the detailed analysis and processing of data from JUNO WAVES instrument,we found a kind of chorus waves located at high L_J and high magnetic latitude.We analyzed and processed the fluctuation data from July 7 2016 to July 122016.The observations indicate that chorus waves occur widely in the region between35-75 R_J（the Jupiter’s radius）within 30°of the magnetic equator.The average amplitude of chorus waves in the Jovian magnetosphere is generally at the level of several pT（1-3 pT）,weaker than that in the terrestrial magnetosphere.Chorus wave intensities at Jupiter are also found to exhibit a tendency of slow increase with increasing L_J and gradual stability with decreasing magnetic latitude.Based on these observational results,we implement fits of exponential power-law function to develop an empirical model of the variation of Jovian chorus wave amplitude with L_J and magnetic latitude.（2）Quantitative determination of the chorus wave driven electron scattering effect in the Jovian magnetosphere requires detailed information of both ambient magnetic field and plasma density and wave spectral property.We therefore perform a comprehensive analysis of the sensitivity of chorus induced electron scattering rates to ambient magnetospheric and wave parameters in the Jovian radiation belts.We find that the ambient magnetic field intensity,the wave latitudinal coverage and the peak frequency and bandwidth of the wave spectral distribution in the Jovian magnetosphere can strongly affect chorus induced quasi-linear electron scattering rates,but the background plasma density profile and the peak wave normal angle not,especially when the wave emissions are confined at low latitudes（e.g.,|λ|<15°）.Given the chorus wave amplitude,chorus induced electron scattering rates strongly depend on Jovian L-shell to exhibit a tendency approximately proportional to³.（3）The dynamic evolution of electrons in Jupiter’s radiation belt under the influence of chorus wave scattering also depends on the electron distribution profiles.We adopt a group of reasonable initial conditions based upon the available observations and models for quantitative analyses.For lower-band chorus,a variable initial pitch angle distribution can cause the electron acceleration of 500 keV and 1 MeV electrons at lower pitch angles,and a very gradient initial energy spectrum distribution can cause1 MeV and 5 MeV electron acceleration at high pitch angles.For upper-band chorus,a variable initial pitch angle distribution can cause the acceleration of 5 keV and 10 keV electrons at lower pitch angles,and a relatively flat initial energy spectrum distribution can cause¹.5–10 keV electron acceleration at high pitch angles.