磁暴期間外輻射带結构的变化

本文根据磁矩守恆的条件,利用刘維定理（Liouville's theorem）,討論了磁暴期間在赤道平面外輻射带內,带电粒子的空間分布及能量分布的变化。結果表明:当主相时,粒子密度及通量的峯值变小而且位置向外移动。此結果与探測事实相符。能譜分布也有显著的变化,不論垂直能量或是平行能量,当主相时能量分布的峯值向低能量的方向偏移;急始时向高能量的方向偏移。对投擲角及鏡点高度作了計算,发現当急始时投擲角变大,而鏡点高度下降;主相吋投擲角变小,镜点高度上升。由此可以訊为,在主相期間緩慢的磁場下降,不能使外輻射带內粒子侵入上层大气。相反,在急始时則可能有一部分粒子会侵入上层大气。根据所得結果,基本上可以解释目前的观測現象。

THE VARIATION OF THE OUTER RADIATION BELT DURING THE MAGNETIC STORM

The effect of large-scale geomagnetic fluctuation on the distribution function of charged particles trapped in the outer radiation belt is investigated with the following main results. （1）During the main phase, the position of maximum electron intensity shifts outwards with decreasing peak intensity, while in the sudden commencement the position of maximum electron intensity moves inwards with increasing peak intensity.This is supported precisely by the measurements of Explorer 6 as well as by the observations of two Soviet Lunar rockets 1 and 2. （2）The variation of the distribution of kinetic energy is likewise very considerable.The peak shifts to the range of smaller energy during the main phase and to the range of higher energy during the initial phase. （3）The pitch angles decrease in the main phase but increase during the initial phase. （4）The altitudes of the mirror point decrease in the initial phase and increase in the main phase. With these findings we come to the following conclusion. Because of the expansion of the tube of force as well as the diminishing of the kinetic energy, the density and hence the intensity of the charged particle on the magnetic equator is reduced during the main phase. While in the initial phase, owing to the descent of the mirror point,a part of the charged particle may precipitate into the lower atmosphere and excite the aurorae, but because of the compression of the tube of force and increase of the particle's kinetic energy, the intensity of the charged particle on the magnetic equator still shows up clearly the tendency of increasing.