磁层压缩ULF湍流对电子的加速  

Electron Acceleration by Compressional ULF Turbulence in the Geomagnetosphere

作　　者：李柳元[1] 曹晋滨[1] 周国成[1] 刘振兴[1] 

机构地区：[1]中国科学院空间科学与应用研究中心

出　　处：《空间科学学报》2005年第1期1-5,共5页Chinese Journal of Space Science

基　　金：国家杰出青年科学基金项目(40025413)重大基金(40390150)共同资助

摘　　要：在准线性理论下，磁层压缩 ULF(超低频)湍流可以通过“渡越时间加速”机制使电子增加能量．典型的压缩 ULF 湍流的频率为2—15mHz，被加速的源电子为同步轨道附近的背景电子(E＜30keV)和亚暴注入电子(30—300 keV)．当发生波粒共振时，低能电子数减少，而高能尾部分的相对论(E≥1 MeV)电子数增加，这说明电子得到了压缩湍流的有效加速，且亚暴注入的电子数越多，其加速产生的相对论电子数也越多．在亚暴注入率ε=0.5的情况下，这种加速机制只要约12h 就可以造成同步轨道附近相对论电子数量的显著增加．In quasi-linear approximation,the electron“transit-time acceleration”by compressionalULF turbulence near the geosynchronous orbit is studied.The frequency range of compressional ULFturbulence is from 2mHz to 15 mHz.When compressional ULF waves resonate with the backgroundelectrons(E<30keV)and substorm injection electrons(30—300keV),the electrons with higher-energy increase while the lower-energy electrons decrease,which showed that resonant electrons areaccelerated effectively by compressional ULF turbulence.The efficiency of the electron accelerationdepends on the character of ULF waves,the larger the amplitude of ULF waves are,the higher theacceleration efficiency is,and the bigger the spectral index is,the lower the acceleration efficiency is.In addition,the more substorm injection electrons are,the more relativistic electrons produced by‘Transit-time acceleration’are.Since substorms can offer substorm injection electrons,therefore largeflux enhancement events of relativistic electrons(E≥1 MeV)always occur during substorm time.For magnetic storms that are composed of a series of substorms,extremely large flux enhancementevents of relativistic electrons can thus occur.

关 键 词：相对论电子 湍流 相对论 压缩 高能 准线 加速 磁层 同步轨道 线性理论 

分 类 号：P353[天文地球—空间物理学]