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    题名: 對電漿系統中帶電粒子束與救火管不穩定性之研究;Streaming and fire hose instabilities in pair plasmas
    作者: 饒駿頌;Jao,Cung-Sung
    贡献者: 太空科學研究所
    关键词: 不穩定性;對電漿;帶電粒子束不穩定性;救火管不穩定性;數值模擬;正子;電漿;electron-positron plasma;fire hose instability;instability;pair plasma;particle simulation;plasma;positron;simulation;streaming instability
    日期: 2013-01-21
    上传时间: 2013-03-25 15:52:18 (UTC+8)
    出版者: 國立中央大學
    摘要: 電漿為物質的第四態。太空環境中的電漿主要由電子與離子所組成,然在高能的環境中,如地球的輻射帶及某些天文系統中,會出現正電子與電子所組成的正負電子電漿,也稱作「對電漿」。相對於電子離子電漿系統,許多現象與機制在「對電漿」系統中仍屬於待研究之問題,而本論文將研究「對電漿」中之帶電粒子束不穩定性與救火管不穩定性。除了建立帶電粒子束靜電場不穩定性的線性流體理論外,本論文首次利用一維靜電場全粒子模式驗證,由正電子與電子共組粒子束進入由正電子與電子共組背景電漿之四元素系統,可形成週期性孤立波結構與交織之正電子洞與電子洞之結構。本論文同時也將粒子模擬過程中的熱力狀態與流體理論相互驗證,並用以解釋不穩定性系統停止生長之機制。另外,二維粒子模擬的研究顯示,一維模擬系統中可以穩定存在的週期性孤立波結構,在二維系統中會因為熱耗散或是垂直磁場傳播之靜電波生成而瓦解。本論文也將探討帶電粒子束電磁場不穩定性與救火管不穩定性的磁場成長機制。首先,利用壓力非均向之雙流體線性理論,得出「對電漿」系統中救火管不穩定性的發生條件與成長速率。一維電磁場全粒子模擬的研究顯示,線性理論中所預測之較大成長速率之短波,在模擬實驗中因為波與粒子迴旋頻率產生之共振效應會自動被抑制。而因帶電粒子束電磁場不穩定性導致磁場成長的效應,則是因為帶電粒子束平行磁場傳播之電磁波與背景電漿中平行磁場傳播之電磁波共振所造成的。電磁場粒子模擬的初始階段亦可觀察到靜電場不穩定性的發生時間比電磁場不穩定性來得早,而雖然靜電場不穩定性的發生會造成系統中的壓力非均向性,但其磁場引發機制與救火管不穩定性並不全然相同,模擬顯示,電磁場帶電粒子束不穩定性的穩定條件趨近於 Beta_pal - Beta_per < 0。Plasma is the fourth state of matter. While electron-proton plasmas may exist in most space plasma environments, electron-positron or pair plasmas may be present in the high energy environments such as the Earth's radiation belt and many astrophysical systems. This thesis studies the streaming and fire-hose instabilities which have not well been explored in pair plasma system. We first examine the electrostatic streaming instability based on the linear fluid theory and address the formation of solitons and hole structures in electron-positron plasmas by using one-dimensional electrostatic particle-in-cell model which demonstrates for the first time the periodic interlacing electron-positron hole structures. The hole structures are generated by current-free electron and positron beams streaming in a stationary electron-positron background plasma. Detailed comparisons between simulation results and linear theory of streaming instability in pair plasmas are made and the thermodynamic state is inferred. In the two-dimensional simulations, the hole structure may decay because of the heat dissipation or the development of electrostatic waves perpendicular to the background magnetic field. This thesis also studies the growth of magnetic field by the electromagnetic streaming and the fire-hose instabilities. The fire-hose instability condition and the growth rate are examined based on the linear anisotropic hydromagnetic theory. It is found that though the waves with shorter wavelengths have larger growth rate based on the linear theory, their growth is restrained due to the gyro-resonance of particles in the nonlinear evolution processes. In the nonlinear evolution processes of electromagnetic streaming instability, the electrostatic instability takes place before the electromagnetic instability making the system anisotropic and triggering the magnetic field growth. The nonlinear simulation results show that the electromagnetic streaming instability saturates at Beta_pal - Beta_per < 0 .
    显示于类别:[太空科學研究所 ] 博碩士論文

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