本論文研究在熱傳導效應下的快震波結構。在磁場重聯的過程中會產生快震波、中速震波及慢震波等不連續結構。發生在日冕區的磁場重聯，則必須考慮其強烈的熱傳導效應，其中產生的慢震波結構已在Tsai et al. [2002, 2005]詳細探討過。利用一維磁流體(1D-MHD)數值模擬碼，研究在不同電漿參數下的快震波結構，這些參數包括：熱傳導係數K0，電漿的壓力與磁壓比，馬赫數，及磁場與法線方向的夾角。為方便震波結構的分析，直接由震波上游參數，結合Rankine-Hugoniot (R-H)關係式計算出下游參數，並分析快震波隨時間的發展。研究發現快震波會在主震波上游近端形成波前震波(foreshock)結構，這是由於震波加熱過的下游電漿，藉由熱傳導效應將熱能從震波下游傳遞到上游，使主震波近處上游的電漿有別於遠方上游的分布而形成波前震波結構。本研究觀察在不同參數下，快震波之波前震波結構隨時間的變化。我們發現，快震波下游電漿受到熱傳導效應的作用，熱能以擴散速度(Vd)由下游傳遞到上游，當Vd與對流速度相同時，快震波即達到穩定狀態。研究並發現在不同K0的情形下其擴散速度(Vd)都大致相同。經由兩個修改的R-H關係式：包含熱流的R-H關係式及等溫條件下的R-H關係式，去計算越過震波的密度躍遷，所得到的計算值和模擬結果非常接近，且密度躍遷可達沒有熱傳導效應影響下的4倍以上。研究結果將可應用到日冕、太陽風及磁層的快震波研究。

The structure of fast shocks in the presence of heat conduction is studied. The fast shock, intermediate shock and slow shock can be generated by magnetic reconnection. The heat conduction effect is important for magnetic reconnection in the solar corona. The structure of slow shocks in the presence of heat conduction has been studied in Tsai et al. (2002, 2005). By using one- dimensional (1D) MHD simulation in this paper. The structure of fast shocks is studied under different plasma parameters, such as the heat conductivity K0, the ratio of upstream plasma pressure to magnetic pressure, Alfvén Mach number, and the angle between shock normal and magnetic field. For the convenience of setting up the initial shock structure. The Rankine-Hugoniot (R-H) relations are used to determine the downstream parameters for a given set of upstream parameters, which are then used to simulate the time evolution of fast shocks. It is found that the fast shock will form a foreshock in the presence of heat conduction. The foreshock is formed due to the heat flow from downstream to upstream and located in the immediate upstream of the main shock. The time evolution of the foreshock structure is simulated under different set of initial upstream parameters. The value of diffusion velocity Vd in the foreshock is found to be approximately equal to the convection velocity of fast shock, and hence the diffusion velocity is nearly the same for different values of K0. By using two kinds of modified R-H relations, the modified Rankine-Hugoniot relations with heat flux, and modified isothermal Rankine-Hugoniot relations, the density jump across fast shock is examined for various upstream parameters. The results show that the calculated density jumps are very close to the simulation values and the density jump can far exceed the maximum value of 4 without heat conduction. The present results can be applied to fast shocks in the solar corona, solar wind and magnetosphere.

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