| DC 欄位 |
值 |
語言 |
| DC.contributor | 太空科學研究所 | zh_TW |
| DC.creator | 余秀珊 | zh_TW |
| DC.creator | Hsiu-Shan Yu | en_US |
| dc.date.accessioned | 2011-7-5T07:39:07Z | |
| dc.date.available | 2011-7-5T07:39:07Z | |
| dc.date.issued | 2011 | |
| dc.identifier.uri | http://ir.lib.ncu.edu.tw:444/thesis/view_etd.asp?URN=93643003 | |
| dc.contributor.department | 太空科學研究所 | zh_TW |
| DC.description | 國立中央大學 | zh_TW |
| DC.description | National Central University | en_US |
| dc.description.abstract | 日珥（或稱暗紋）噴發及日冕拋射物質常在迅速的加速之後伴隨著等速度傳播。相較於大尺度的日冕拋射物質，太陽閃焰為一小尺度的局部現象。過去的觀測結果顯示，由閃焰發生處的磁場環狀結構的足點運動及垂直太陽表面的正向磁場，所計算得出的磁場重聯率與日冕拋射物質之加速度在時間上有很好的正相關性[Zhang et al., 2001; 2004; Qiu et al., 2004; Jing et al., 2005]。本論文即利用加了磁場耗散效應的二維磁性流體模擬碼來研究(1)磁場重聯隨時間變化及其與電漿流加速的關聯性，(2)造成電漿流及電漿團的加速作用力，以及(3)磁通量變化對磁重聯率的影響。我們的研究結果顯示，磁場重聯後的快速流並不侷限在垂直磁場方向。平行磁場方向的快速流是由平行磁場的壓力梯度力所加速。而垂直磁場的淨力除了加速電漿流外，亦會加速電漿團。而電漿團的加速度除了受作用力影響外亦受電漿團內的質量所控制。我們發現磁性流體中的磁場重聯效應是由電流片中磁場消滅程度不均勻所造成的。磁場重聯的點並不侷限在中性點上，反而會隨著電流分叉的Y點移動。我們的研究也發現電漿團的快速噴射效應會拉長電流片進而暫時減緩磁場重聯速率，直到新的電漿團形成後，才會再度提昇磁重聯率。因此我們提出磁場重聯與電漿團加速作用之間的耦合理論：磁場重聯所產生的磁張力會加速電漿團，然而，快速移動的電漿團會拉長電流片進而降低磁場重聯率，但同時被拉長的電流片又會引發新的磁重聯，造成更多小尺度且高速移動的電漿團。同時我們也發現電漿團的最大移動速率會隨著它的大小和其中電漿的總質量增加而減少。
| zh_TW |
| dc.description.abstract | Prominence/filament eruptions and coronal mass ejections (CMEs) usually show an initial acceleration followed by a nearly constant propagation speed. Concerning about solar flares, it is a local feature in comparison with global feature of the initiation of CME. The magnetic reconnection rate deduced from the foot point motions of the solar flares and the magnetic field component normal to the solar surface and the acceleration of filament/CME show a good temporal correlation [Zhang et al., 2001; 2004; Qiu et al., 2004; Jing et al., 2005]. In this thesis, a two-dimensional resistive magnetohydrodynamic (MHD) simulation is carried out to study (1) the time evolution of the magnetic reconnection and its relation to the acceleration of plasma flow, (2) the forces that lead to the acceleration of the plasma and the plasmoid, and (3) the rate of magnetic flux variation effects on the reconnection rate. Our results show that the fast flows are not limited to the direction perpendicular to the local magnetic field. The fast parallel flows are accelerated by the parallel component of the pressure gradient force. The net force perpendicular to the magnetic field can accelerate the plasma and the plasmoid along the current sheet. The acceleration of the plasmoid is also controlled by the mass contained in the plasmoid. We found that the magnetic reconnection in MHD plasma is due to the non-uniform magnetic annihilation rate along the current sheet. The reconnection/reconfiguration site does not necessary stay at the neutral point. It can move with the Y-line next to the bifurcated current sheets. We also found that the fast ejection of the plasmoid can stretch the current sheet and consequently reduce the magnetic reconnection/reconfiguration rate temporally before a new plasmoid is formed. A mutual coupling theory of magnetic reconnection and acceleration of plasmoid is proposed: the magnetic tension force resulting from the magnetic reconnection will lead to the acceleration of plasmoid; however, the acceleration of plasmoid can stretch the current sheet and reduce the magnetic reconnection rate. But the stretched thin current sheet is favorable for the formations of small scale plasmoids. We also found that the speed of the plasmoid increases with decreasing the size of the plasmoid.
| en_US |
| DC.subject | 數值模擬 | zh_TW |
| DC.subject | 電漿團加速 | zh_TW |
| DC.subject | 磁場重聯 | zh_TW |
| DC.subject | 磁流體力學 | zh_TW |
| DC.subject | resistive MHD | en_US |
| DC.subject | acceleration of plasma | en_US |
| DC.subject | magnetic reconnection | en_US |
| DC.subject | acceleration of the plasmoid | en_US |
| DC.subject | magnetohydrodynamic simulation | en_US |
| DC.title | 磁流體力學中電漿團加速與磁場重聯率變化成因之數值模擬研究 | zh_TW |
| dc.language.iso | zh-TW | zh-TW |
| DC.title | Simulation Study of the Causes of Plasmoid Acceleration and the Changes of Magnetic Reconnection Rate in Resistive MHD Plasmas | en_US |
| DC.type | 博碩士論文 | zh_TW |
| DC.type | thesis | en_US |
| DC.publisher | National Central University | en_US |