本研究先建立起MS模式的模擬碼，用以研究磁層中各種電漿波的性質，及
其不穩定現象。今利用所建立之靜磁模式模擬出雙流不穩性，在外加磁場
由弱變強下的變化情形。由研究中得知，當磁場強度強時，雙流不穩定中
，波與粒子的交作用較不顯著。

In this paper, the simulation code of MS Model is established
to study the properties of different plasma waves and
instabilities in the magnetosphere. By using the established
MS Model, the variation of the two stream instability under the
influence of the external magnetic field are simulated. It is
found that when the external magnetic field is strong, the wave-
particle interaction of the two stream instability is not
significant.