中速震波生成之模擬研究

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Title:	中速震波生成之模擬研究
Authors:	賴淑華;Shu-Hua Lai
Contributors:	太空科學研究所
Keywords:	震波;模擬;電漿;shock wave;simulation;plasma
Date:	2000-07-05
Issue Date:	2009-09-22 09:45:04 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	行星際空間中，太陽風在地日關係裡扮演著一個非常重要的角色，使行星際介質分布不均勻而產生各種磁流體波、不連續面和震波。先不討論線性波動，僅就震波和不連續面而言，就有快速震波(FS)、慢速震波(SS)、中速震波(IS)、旋轉不連續(RD)、切線不連續(TD)、接觸不連續(CD)。一般而言，快速震波及慢速震波均為可壓縮波，此類波動可經由陡峭作用而生成快速震波及慢速震波，但是Alfven wave 確是不可壓縮波，所以中速震波無法經由Alfven wave陡峭而形成，故本論文研究主題便著重在中速震波的形成。1993年趙寄昆教授發表第一個中速震波的實際觀測資料，並以慢速震波和接觸不連續相互作用模擬出雷同的中速震波結構。本文即採用這個生成機制作更詳細的參數設定以假設不同的太空環境，希望找到最適合中速震波生成的條件。模擬後發現此機制只能生成type 2à4及type 1à4的中速震波，並發現某些type 2à4的中速震波再與接觸不連續碰撞後會演變成type 2à3的中速震波，其原因值得再進一步以理論加以探討。本文也模擬快速震波與接觸不連續碰撞，發現無法生成中速震波，藉此結果以比較中速震波由CD-SS此物理機制生成之原因。 In the solar-terrestrial relationship, the solar wind plays an important role to generate different kinds of MHD discontinuities and shocks. Let aside of the linear wave, there are FS, SS, IS, RD, TD, and CD in the classification of the shocks and discontinuities. Generally speaking, both of the fast wave and slow wave are compressible and they can produce the fast shock and slow shock by the steepening effect. On the other hand, the Alfven wave is incompressible, so it can’t produce the intermediate shock by the steepening process. Thus we focus on the generation of intermediate shock. In 1993, Prof. Chao find a intermediate shock event on the real space plasma data, and then by using MHD and Hybrid simulation found a intermediate shock structure the same as the data of observation after CD-SS interaction. Depend on this mechanism of generation, we change initial values to image different space environments and wish can find the suitable conditions of generation on intermediate shock. But this mechanism only produce type 2à4 and type 1à4 intermediate shock. After some type 2à4 intermediate shocks collide with CD once again, these type 2à4 intermediate shocks change into type 2à3. We will investigate these phenomena in the future by the theoretical study. We also simulate the interaction of fast shock and CD, but this mechanism can’t produce intermediate shock and use the results to compare and analyze the causes of generation on intermediate shock.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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