Laboratory Experiments on Electrostatic Potential Structure concerned with Aurora Phenomenon

了解极光现象对于阐明地球磁层的动力学特征是非常重要的。电子加速引起极光放电的原因是等离子体电位沿极光椭圆上方磁场线的沿着倾斜。本文测量了极光等离子体中沿磁场线沿着的孔隙形成。在强轴向磁场的作用下，利用2300 K高温钨板表面电离k原子产生的无碰撞等离子体，被约束在一个镜像位形的磁场中。等离子体流速V在V_o/C_s（C_s：离子声速）的较宽范围内变化。在磁力线会聚的区域，等离子体电势增加，这与基于电子和离子不同俯仰角的理论预测一致。然而，当等离子体前沿到达终板时，我们认识到终板的一个很大的影响，即，对于终板的正偏置电势，等离子体电势的增加显著增强。电势剖面的三维结构显示出穿过磁场的大电场，类似于极光椭圆上方的电场。

It is quite important to understand aurora phenomena in order to clarify a dynamic feature of the Earth's madnetosphere. Electron acceleration inducing auroral discharge has been supposed to be due to a plasma potential slope along the magnetic field lines above the auroral ovalIn this work, measurements were performed on porenrial formation along the mahnetic field lines in a loboratory plasma. A collisionless plasma, produced by surface ionization of k atoms on a hot tungsten plate heated up to about 2300k, was confined by a strong axial magnetic field with mirror configuration. The plasma flow speed V was varied in the wide range of V_o/C_s(C_s: ion acoustic speed)The plasma potential is found to increase in the region where the magnetic field lines are converged, being consistent with theoretical prediction based on different pitch angles of electrons and ions. When the plasma front reaches the endplate, howevwe, a big effect of the end- plate is recognized, i.e., for a positive bias potential of the endplate, the plasma potential increase is drastically enhanced. Three-dimensional structure of the potential profile shows a large electric field across the magnetic field, being similar to that above the auroral oval.