主动空间试验中空间电荷波向电磁波的转换  

Transformation of space-charge wave to electromagnetic wave in active space experiments

作　　者：杨勇[1] 赵正予[1] 王艳[1] Anisimov I O 

机构地区：[1]武汉大学电子信息学院,武汉430079 [2]乌克兰基辅国立舍辅琴科大学无线电物理系,基辅01033

出　　处：《地球物理学报》2007年第2期338-345,共8页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(40374059)资助

摘　　要：本文理论分析了电子束沿地磁场穿越均匀、磁化等离子体密度跃变区域时,在弱磁场近似、哨声波激发、低频近似等几种典型情况下电子束流空间电荷波(Space-charge wave)向电磁波的转换.先运用小信号假设求得电子束入射进均匀各向异性冷等离子体之后的色散关系和空间电荷波波数,然后借助于电磁波分量和电子束速度的边界条件,求解电子束在等离子浓度发生变化区域激发的波振幅,在几种典型情形下推导出空间电荷波转换为电磁波之间转换系数的近似解,给出了相应波辐射的坡印亭(Poynting)矢量表达式.结果表明,在渡越辐射(Transition radiation)情形下电子束可以在空间等离子体中激发出阿尔芬波(Alfven wave)和哨声波(Whistler wave).所得结论可用于对主动空间试验结果的分析.We have analyzed the transformation from the space-charge wave into the electromagnetic wave when electron beams pass through the concentration step of cold anisotropic plasma along the geomagnetic field. We focus our analysis on several typical conditions such as weak magnetic field approximation, whistler wave excitation, and low frequency approximation. We first derive the dispersion relation and the wave number of the space-charge wave under small signal assumption, and then calculate the amplitude of the wave excitation in the concentration step of the plasma, using the electromagnetic component and the boundary condition of the velocity of the electron beam. We obtain the approximate solution to the coefficient of the transformation from the spacecharge wave into the electromagnetic wave, and provide the Poynting vector presentation of the corresponding wave radiation. We have demonstrated the principle possibility of the Alfven wave and Whistler wave excitation in inhomogeneous plasma by the modulated electron beam with transition radiation mechanism. These results can be used to analyze experimental data collected in active plasma experiments in space.

关 键 词：空间电荷波 渡越辐射 阿尔芬波 哨声波 

分 类 号：P352[天文地球—空间物理学]