多离子空间等离子体中快磁声波与粒子的回旋共振特性

摘要

快磁声波是空间等离子体中一种接近垂直传播的右旋极化电磁波,能够在等离子体层内外传播.快磁声波与带电粒子的回旋共振相互作用能够导致高能电子随机加速和投掷角扩散、能量质子投掷角扩散等,从而影响辐射带高能带电粒子的动态过程.分别基于完整的色散关系和高密度近似的色散关系,在不同空间等离子体条件下研究多离子空间等离子体中不同传播角的快磁声波色散曲线,并计算了快磁声波与H+,He+和O+离子的最小共振能量.结果表明,当传播角较小时,采用高密度近似与采用完整色散关系计算的离子最小共振能量没有太大差别.在中低密度中强磁场空间等离子体中,传播角≥88°时高密度近似色散关系会带来很大的误差,因此应利用完整色散关系计算最小共振能量.%Fast Magnetosonic (MS) waves are right-hand polarized waves.They propagate both inside and outside the plasmasphere,and the wave vectors are almost perpendicular to the ambient magnetic field.Fast MS waves can lead to local electron acceleration,scattering of outer radiation belt energetic electrons,and scattering of energetic protons etc.Using the fully and high-density approximated dispersion relations,the dispersion curve of fast MS with different wave normal angle is analyzed,and the minimum resonant energy between MS waves and ions (H+,He+,and O+) are calculated.The results show that,as the wave normal angle is relatively small,the minimum resonant energy obtained by the high-density approximated and fully dispersion relation is quite close to each other in a high density and weak magnetic field space plasma.Remarkable error occurs when the high-density approximated dispersion relation is used in the low and medium density space plasma or when the wave normal angle is greater than 88°.Therefore,the fully dispersion relation must be used in these cases.