Theory on Spiral Structure Formation in Magnetized Plasmas

研究了旋转等离子体中密度空穴的形成过程，得到了相应的定态解。与离心力和气压相互平衡的台风相反，观测到的空洞具有与Burgers涡旋相似的结构。根据这一观察结果导出了定态解。那么，由理论定态解与观测到的空穴相吻合的参数得到的粘度比由碰撞过程估算的粘度大10^6个数量级。然而，旋转是由E × B漂移决定的，而E × B漂移是由电势决定的。因此，使用实验中观察到的势分布的唯象方法不仅给出了密度分布，而且给出了与观察结果一致的速度场和涡度。有趣的是，尽管Burgers涡场在无穷远处发散，但在旋转轴附近速度场与Burgers涡场一致，在远离涡轴处速度场消失。这表明，在磁化等离子体中，等离子体空穴与螺旋结构属于同一类自组织。该三极涡旋以与E x B旋转相反的方向旋转。这种旋转是由离子和中性粒子之间的电荷交换引起的动量转移引起的漂移。一个固定的三极涡的解决方案已获得和参数的选择，使解决方案显示出最佳的配合与所观察到的三极涡。然而，我们还没有检查的稳定性的定常三极涡的解决方案。

We studied the processes of plasma density hole formation observed in a rotating plasma and obtained corresponding stationary solution. On the contrary to typhoon for which centrifugal force and pressure are balanced with each other, the observed hole has similar structure to the Burgers vortex. The stationary solution has been derived based on this observation. Then the viscosity obtained from the parameters for which the theoretical stationary solution fits the observed hole is larger by order of 10^6 than the viscosity estimated from collisional processes. However the rotation is stemed from E x B drift which is determined by the potential. Thus a phenomenological approach for which the potential profile observed in the experiments is used gives not only the density profile but also the velocity fields and vorticity which coincide with the observations. Interesting things are that the velocity fields agree the Burgers vortex field in the vicinity of the rotation axis and vanish at the far distance from the vortex axis although the Burgers vortex field diverges at infinity. This shows the plasma hole belongs to the same class of self-organization in magnetized plasma as the spiral structure.In the same experimenta device a tripole vortex is also observed. This tripole vortex rotates in an opposite direction to E x B rotation. This rotation is identified with the drift induced by the momentum transfer due to charge exchange between ions and neutral particles. A stationary tripole vortex solution has been obtained and parameters are shown to be chosen so that the solution shows the best fit with the observed tripole vortex. However we have not checked the stability of the stationary tripole vortex solution.