磁层磁声波对辐射带电子的加速作用:试验粒子初步研究

【作者】 李金星； 濮祖荫； 谢伦； 付绥燕； 宗秋刚； 倪彬彬； R.Thorne； J.Bortnik； L.Q.Ma；

【Author】 R.Thorne;J.Bortnik;L.Q.Ma;Department of Atmospheric and Oceanic Sciences,University of California,Los Angeles,California;

【机构】 北京大学空间物理与应用技术研究所； Department of Atmospheric and Oceanic Sciences,University of California,Los Angeles,California；

【摘要】 Quasi-linear theory has been used to study resonant interactions between radiation belt energetic electrons and magnetosonic(MS)waves for an intense wave event[Horne et al.,2007],and recently based upon a statistical THEMIS wave survey during solar minimum[Shprits et al.,2013].Test particle simulations for MS wave-electron interactions[Bortnik et al.,2011]also reported that,transit time scattering,which is weaker than Landau-resonance scattering,can also diffuse and accelerate electrons.In the present study,the rates of scattering radiation belt electrons due to interactions with broadband MS waves at multi-frequencies are evaluated for the first time using test particle simulations,which are then compared to the results obtained using quasi-linear theory.We find nice agreement on the diffusion rates between quasi-linear theory and test particle simulations for MS-electron interaction near Landau resonance.While recent statistical analysis suggests that averaged electron scattering rates by MS waves during solar minimum are well below those by whistler-mode chorus and plasmaspheric hiss,here we demonstrate,through theoretical and numerical analyses,that MS waves is capable of effectively scattering and accelerating radiation belt electrons in cases of either strong wave amplitude,high frequency,low wave normal angle,high background plasma density,or in combination of above.We also investigate the long-time evolution of near-equator mirroring electrons with the presence of broadband MS waves,the results of which show that,away from the Landau resonance region,interactions with MS waves tend unable to scatter these near-90°pitch angle electrons because of no resonance or no accumulative transit-time scattering.更多还原

【Abstract】 Quasi-linear theory has been used to study resonant interactions between radiation belt energetic electrons and magnetosonic(MS) waves for an intense wave event [Horne et al.,2007],and recently based upon a statistical THEMIS wave survey during solar minimum [Shprits et al.,2013].Test particle simulations for MS wave-electron interactions [Bortnik et al.,2011] also reported that,transit time scattering,which is weaker than Landau-resonance scattering,can also diffuse and accelerate electrons.In the present study,the rates of scattering radiation belt electrons due to interactions with broadband MS waves at multi-frequencies are evaluated for the first time using test particle simulations,which are then compared to the results obtained using quasi-linear theory.We find nice agreement on the diffusion rates between quasi-linear theory and test particle simulations for MS-electron interaction near Landau resonance.While recent statistical analysis suggests that averaged electron scattering rates by MS waves during solar minimum are well below those by whistler-mode chorus and plasmaspheric hiss,here we demonstrate,through theoretical and numerical analyses,that MS waves is capable of effectively scattering and accelerating radiation belt electrons in cases of either strong wave amplitude,high frequency,low wave normal angle,high background plasma density,or in combination of above.We also investigate the long-time evolution of near-equator mirroring electrons with the presence of broadband MS waves,the results of which show that,away from the Landau resonance region,interactions with MS waves tend unable to scatter these near-90° pitch angle electrons because of no resonance or no accumulative transit-time scattering.更多还原