等离子体性质对磁泡的影响

Effect of plasma properties on magnetic bubbles

利用三维混合模拟程序计算了大量超热碎片离子在低密度背景等离子体中爆炸膨胀的过程.通过定量计算磁泡的变化过程和磁泡对碎片云运动的约束效果,分析了背景等离子体电荷密度、背景离子原子量、碎片离子荷质比等参数对磁泡的影响.计算结果表明,背景电荷密度对磁泡和碎片云的运动有重要影响.在碎片云扩张早期,背景离子原子量对磁泡扩张影响较小,但对后期碎片云的运动有一定影响.当碎片离子荷质比较小时,离子回旋半径大于磁泡半径,此时磁泡半径较小,且磁泡无法约束碎片云.当碎片离子荷质比较大时,离子回旋半径小于磁泡半径,如果此时背景电荷密度较低,磁泡和碎片云的早期扩张几乎不受碎片离子荷质比影响,但对系统后续演化有一定影响,如果此时背景电荷密度较大,碎片离子荷质比对磁泡和碎片云的运动有较大影响.

In this work,a three-dimensional hybrid simulation program is used to investigate the process of the explosion and expansion of a large number of thermal debris ions in a low density background plasma.By quantitatively calculating the variation of the magnetic bubble and the bubble constraint in the motion of the debris cloud,studied are the influences of the background plasma charge density,the background ion atomic weight,and the charge-mass ratio of the fragment ion on the magnetic bubble.The results show that the background charge density has an important effect on the motion of the bubble and debris cloud.In the early stage of the debris cloud expansion,the background ion atomic weight has little effect on the bubble expansion,but it affects the movement of debris cloud at a later time.When the charge-mass ratio of the debris ion is small,the radius of the ion gyration is larger than the bubble radius,and the bubble radius is small so that it cannot restrain the debris cloud.When the charge-mass ratio of the debris ion is large,the radius of the ion gyration is smaller than the bubble radius.If the background charge density is low in this condition,the early expansion of the bubble and the debris cloud are slightly affected by the charge-mass ratio of the fragment ions,and only the subsequent evolution of the system is influenced.If the background charge density is large in this condition,the charge-mass ratio of the fragment ion has a prominent influence on the motion of the bubble and the debris cloud.