磁尾粒子在晨昏电场作用下的散射与沉降

我们认为,在沉降粒子的形成中,磁尾粒子的散射是极其重要的。本文从粒子的轨道理论人手,通过对近900条粒子轨道的具体计算,研究了磁尾粒子在晨昏电场作用下的投掷角变化。计算结果清楚地显示出了磁尾粒子在晨昏电场的作用下,经历着明显的散射过程。运动经过非小扰动区的磁尾粒子在非小扰动区内经多次反射,磁矩不再是不变的,从而投掷角改变,使得一个原在磁尾为各向同性的投掷角分布,在粒子运动到远离中性线的近地区域时改变成为一个近麦氏分布。我们还研究了这些粒子的空间经历,发现这些离开磁尾进入近地区域的粒子在发生散射的同时还发生了空间分离——晨昏分离、纬向分离以及质子和电子之间的相对空间分离,给出了清晰的粒子沉降图象。 

SCATTERING AND PRECIPITATING OF PARTICLES OF THE MAGNETOTAIL UNDER THE ACTION OF THE DAWN-DUSK ELECTRIC FIELD

We think that scattering of particles of the magnetotail in forming of precipitating particles is very importment.In this paper,the pitch angle changing of charged particles of the magnetotail under the action of the dawn-dusk electric field is studied by evaluating about 900 trajectories by computer.The results show clearly that the charg-ed particles of the magnetotail under the action of the dawn-dusk electric field undergo evident scattering process.The particles of the magnetotail which move through the nonperturbation region are reflected many times inside the nonperturbation region,the magnetic moment is no longer invariant,and when they leave the nonperturbation region,their pitch angles are changeable.This change makes isotropic initial pitch angles distribution change into a Maxwellian state,when the particles are away from the neutral line and enter into the region of near earth.The space career of these particles are also studied,and it is found that they undergo space separation (dawn-dusk separation,latitude separation and a relative separation between the protons and electrons) when they leave the magnetotail and enter into near earth with the clear precipiting pattern of the particles.