高β低碰撞性等离子体中Alfvénic微扰振幅的严格极限
A stringent limit on the amplitude of Alfvénic perturbations in high-beta low-collisionality plasmas
摘要：
结果表明，低碰撞等离子体不能支持线性偏振剪切阿尔文波动超过一个临界振幅$δB_{\perp}/B_{0} \sim β^{\,-1/2}$，其中$β$是热磁压力的比例。在这个截止值以上，发展中的波动将产生压力各向异性，其足以通过平行消防水龙带不稳定性使其自身不稳定。这导致波的频率接近零，在任何振荡之前中断波动。磁场线迅速松弛成一系列角形之字形结构。剪切阿尔芬波振幅的这种限制性范围对许多天体物理等离子体中普遍存在的高$β$条件下的磁化湍流物理学以及$\sim 1 \mathrm{AU}$（其中$β\gtrsim 1$）的太阳风具有深远的影响。
英文摘要：
It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude $δB_{\perp}/B_{0} \sim β^{\,-1/2}$, where $β$ is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfvén-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-$β$ conditions prevalent in many astrophysical plasmas, as well as for the solar wind at $\sim 1 \mathrm{AU}$ where $β\gtrsim 1$.
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