Laboratory Experiments on Electrostatic Potential Structure concerned with Aurora Phenomenon

理解极光现象对于弄清地球狂热圈的动态特征是非常重要的。电子加速引起极光放电被认为是由于沿极光椭圆形上方磁力线的等离子体势斜率。在这项工作中，测量了沿磁力线的极光等离子体中的孔雀的形成。在加热到约2300K的高温钨板上，由K原子表面电离产生的无碰撞等离子体受到镜面结构的强轴向磁场的限制。等离子体流动速度V在较宽的V_o/C_S(C_S：离子声速)范围内变化。在磁力线汇聚的区域，等离子体势能增大，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端板时，我们认识到端板的一个很大的效应，即对于端板的正偏压，等离子体电位的增加急剧增加。电势分布的三维结构显示出一个跨越磁场的大电场，类似于极光椭圆形上方的电场。

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.