太阳高能粒子激波加速能谱的统计分析:ACE观测  

Statistical analysis of the energy spectra of shock accelerations of solar energetic particles:ACE observations

作　　者：童恭圣 何宏青 罗洁 李景 TONG GongSheng;HE HongQing;LUO Jie;LI Jing(School of Mathematics and Statistics,Changsha University of Science and Technology,Changsha 410114,China;Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]长沙理工大学数学与统计学院,长沙410114 [2]中国科学院地质与地球物理研究所地球与行星物理院重点实验室,北京100029 [3]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地球物理学进展》2024年第3期896-904,共9页Progress in Geophysics

基　　金：中国科学院战略性先导科技专项(B类先导专项,XDB41000000);国家自然科学基金委项目(41874207);湖南省研究生科研创新项目(CX20210819)联合资助。

摘　　要：太阳高能粒子对地球空间环境有着重要影响。太阳高能粒子的扩散激波加速(DSA)是指粒子在激波上下游区域来回散射并多次穿越激波面而获得能量的过程。在本工作中,我们使用ACE飞船在1 AU处的47.0 keV~4.8 MeV高能粒子数据,研究了1998—2014年间1AU附近76个行星际激波的离子加速过程.在所选的60个准垂直(16个准平行)激波事件中,约88.33%(81.25%)、48.33%(43.75%)分别在47.0 keV和4.8 MeV处显示了显著的离子通量增强(J_(D)/J_(A)>1.5),其中J_(D)和J_(A)分别是激波下游和上游的背景太阳风中的离子通量。在我们所考虑的激波参数中,J_(D)/J_(A)(J_(D))均与磁场压缩比r_(B)的正相关性最高。通过统计分析,我们量化了影响高能离子能谱的可能因素。结果表明,在我们所选取的激波和等离子体参数中,激波压缩比r与下游能谱指数s_(E,d)的相关性最弱。这一点与经典的DSA理论预测的能谱指数结果形成鲜明的对比。上游太阳风速度V_(sw)与下游离子能谱指数s_(E,d)的相关性最大,并且s_(E,d)随着上游太阳风速度V_(sw)的变化呈现出类似反比例函数的下降趋势,开始下降快然后变缓。此外,结合其他可能因素的分析,可以看出激波加速离子的能谱是多个因素共同作用的结果,而不是仅依赖于某一个因素。Solar Energetic Particles (SEPs) significantly affect terrestrial space environment.Diffusive Shock Acceleration (DSA) of SEPs is the process in which particles are scattered in the upstream and downstream regions of the shock and cross the shock multiple times to gain energy.In this work,we use the data of energetic particles of 47.0 keV~4.80 MeV measured by Advanced Composition Explorer (ACE) spacecraft at 1AU,to investigate the ion acceleration process of 76 interplanetary shocks at 1 AU from 1998 to 2014.Among the selected 60quasi-perpendicular (16 quasi-parallel) shock events,about 88.33%(81.25%) and 48.33%(43.75%) of the events display significant increases of ion fluxes (J_(D)/J_(A))for the energy channels 47.0 keV and 4.8 MeV,respectively,whereJ_(D)andJ_(Arepresent) the ion fluxes in the downstream region of the shocks and in the ambient solar wind,respectively.Among the shock parameters considered,bothJ_(D)/J_(A)(J_(D)) are most correlated with the magnetic field compression ratior_B.Through statistical analysis,we quantify the possible factors affecting the energy spectra of high-energy ions.The results show that among all the shock parameters and plasma parameters,the correlation between shock compression ratiorand downstream energy spectrum indexs_(E,d)is the weakest,which is in sharp contrast with the energy spectrum index results predicted by classical DSA.The correlation between upstream solar wind velocityV_(sw)and downstream ion energy spectrum indexs_(E,d)is the strongest,and the variation ofs_(E,d)with upstream solar wind speedV_(sw)is similar to an inverse proportional function.The decline rate is large at the beginning and then becomes small.In addition,combining the analysis of other possible factors,we can show that the energy spectrum of shock-accelerated ions is the result of the coupled effects of multiple factors,rather than relying on one single factor.

关 键 词：粒子加速 激波 太阳高能粒子 空间等离子体 

分 类 号：P354[天文地球—空间物理学]