周期静磁平衡的自发衰变
Spontaneous decay of periodic magnetostatic equilibria
摘要：
为了理解导致高度磁化的相对论等离子体变得不稳定的条件，以及在这种情况下等离子体如何演化，我们研究了一类典型的静磁平衡，其中磁场满足$\nabla \times\mathbf B = α\mathbf B$，其中$α$是空间均匀的，在一个周期域。使用数值解，我们表明，这种平衡的一般例子是不稳定的理想模式（包括不可压缩的），其标志是指数增长的线性阶段。我们的不稳定模式的特点，显示它如何可以被理解的合并的磁和电流结构，并明确证明其不稳定性使用的能量原理。这些解决方案的非线性演化之后，我们发现，他们迅速发展的区域相对论速度和电场的大小相当的磁场，释放磁能的动态时间尺度，并最终解决到一个配置的最大允许波长。这些性质使这种解决方案成为探索极端宇宙伽马射线源背后机制的一个有希望的环境。
英文摘要：
In order to understand the conditions which lead a highly magnetized, relativistic plasma to become unstable, and in such cases how the plasma evolves, we study a prototypical class of magnetostatic equilibria where the magnetic field satisfies $\nabla \times\mathbf B = α\mathbf B$, where $α$ is spatially uniform, on a periodic domain. Using numerical solutions we show that generic examples of such equilibria are unstable to ideal modes (including incompressible ones) which are marked by exponential growth in the linear phase. We characterize the unstable mode, showing how it can be understood in terms of merging magnetic and current structures, and explicitly demonstrate its instability using the energy principle. Following the nonlinear evolution of these solutions, we find that they rapidly develop regions with relativistic velocities and electric fields of comparable magnitude to the magnetic field, liberating magnetic energy on dynamical timescales and eventually settling into a configuration with the largest allowable wavelength. These properties make such solutions a promising setting for exploring the mechanisms behind extreme cosmic sources of gamma rays.
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