在本篇論文中，我們研究在離子流中帶電粒子之間的交互作用。離子流的速度，是設定在離子以及電子的熱速度之間 （mesothermal condition）。我們將帶電粒子其視為點電荷。我們用一個包含流動離子及波茲曼電子的線性模型，得出有關這個系統的流體力學方程式以及泊松方程式（Poisson’s equation）。經由這些線性方程式的解，找出空間中的電位以及離子密度如何分布，再進一步由此得知帶電粒子的交互作用。我們發現離子的溫度是一個很重要的參數。當溫度為零的時候，電位的最低點會發生在粒子的正後方，因此兩顆粒子會沿著離子流的方向，排列成一直線；而當離子溫度高於某個臨界值後，電位的最低點便不再位於粒子的正後方，粒子間也因此不會再沿著離子流方向排成直線。而在粒子後方，由於離子密度的疏密不同，會產生類似聲波的結構，我們發現無論超音速或是低於音速的離子流，對於這種類聲波的行為，只會造成定量上的差異。 In this thesis the interactions between charge particles inside an ion ow areinvestigated. The ion ow is assumed in the mesothermal condition such that the ion ow velocity v0 is in the regime of vTi << v0 << vTe , where vTi and vTe are the ion and electron thermal velocities respectively. We treat the charge particles as point charges, and apply a linear two- uid model containing owing ions and Boltzmann electrons. The electrostatic potential and the ion density distribution around charge particles are found by solving the uid equations together with the Poisson's equation. Inter-particle interactions are then inferred by the electrostatic potential. We nd that upstream potential induced by a charge particle is always repulsive. On the other hand, a potential minimum is present behind the particle. The ion temperature is an important parameter. For a zero ion temperature, the potential minimum induced always locates directly behind the chaege particle along the ion ow direction. If another particle is present, they will thus align to the direction of the ion ow. For an ion temperature higher than a critical value, the potential minimum does not occur directly behind the charge particle and the two particles no longer align with the ion ow. The structures of the ion acoustic waves created behind the charge particle are also studied. A supersonic ion ow makes only quantitative dierence with the subsonic case in the behavior of the ion acoustic waves.
