再论相对论撕裂不稳定性的增长率：非理想磁流体动力学结构的作用
Revisiting the Growth Rate of the Relativistic Tearing Instability: The Role of the Non-ideal MHD Structure
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中文总结 AI 辅助
针对磁主导对等离子体中的相对论撕裂不稳定性，采用外推A近似修正非理想MHD区域的矢势扰动处理，提升了最不稳定波数的预测精度，为相关天体物理研究提供了更新基准。
中文摘要 AI 辅助
在磁主导的对等离子体中，磁重联是高能天体物理系统中的关键过程。我们重新研究了Harris电流片中的相对论撕裂不稳定性，并推导了其线性增长率与最不稳定波数的改进解析表达式。关键修正在于对非理想磁流体动力学（MHD）区域中矢势扰动的处理：摒弃传统的常A近似，采用外推A近似，即将理想MHD解线性外推至非理想区域。与二维粒子模拟（PIC）的对比显示，该修正理论提升了对最不稳定波数的预测精度，且在低粒子漂移速度下改进最为显著——此时粒子回旋半径小于电流片厚度，最快增长模式向更长波长偏移。所得解析表达式为磁主导重联及其在伽马暴、快速射电暴等高能天体物理等离子体中的应用提供了更新的基准。
英文摘要
Magnetic reconnection in magnetically dominated pair plasmas is a key process in high-energy astrophysical systems. We revisit the relativistic tearing instability in a Harris current sheet and derive an improved analytical expression for its linear growth rate and the most unstable wavenumber. The key modification is the treatment of the vector potential perturbation in the non-ideal magnetohydrodynamic (MHD) region. Instead of the conventional constant-A approximation, we use an extrapolated-A approximation, in which the ideal-MHD solution is linearly extrapolated into the non-ideal region. Comparison with two-dimensional particle-in-cell simulations shows that the revised theory improves the prediction of the most unstable wavenumber. The improvement is most pronounced at low particle drift velocities, where the particle gyroradius is smaller than the current-sheet thickness and the fastest-growing mode shifts to longer wavelength. The resulting analytical expressions provide an updated benchmark for magnetically dominated reconnection and its applications to high-energy astrophysical plasmas, including gamma-ray bursts and fast radio bursts.
