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arXiv 2204.06232astro-ph.SR
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太阳大气中的非理想有限拉莫尔半径效应

The non-ideal finite Larmor radius effect in the solar atmosphere

B. P. Pandey, Mark Wardle

备注：
17 pages, 12 figures, MNRAS (in press)
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摘要：

部分电离的太阳大气动力学是由占主导地位的中性氢原子和带电离子之间频繁的碰撞和电荷交换控制的。在低于碰撞或电荷交换频率的信号频率下，带电粒子和中性粒子同时感受到磁应力{ \it}。离子的中性质量负载导致有效离子-回旋频率的重新缩放-它变成霍尔频率，并且所得的有效拉莫尔半径变成几公里的量级。因此，有限拉莫尔半径（FLR）效应，表现为离子和中性压力应力张量在宏观尺度上运作。而平行和垂直（相对于磁场）的粘性动量传输竞争的欧姆和霍尔扩散的磁场在光球-色球，陀螺粘性效应变得重要，只有在色球和日冕之间的过渡区，它与双极扩散竞争。波在回旋粘性效应主导的介质中的传播取决于等离子体$β$（热能和磁能的比率）。自由能的丰富使陀螺波不稳定的起始条件正好相反的霍尔不稳定性。然而，最大增长率是相同的霍尔不稳定性。对于流动梯度$\sim 0.1 \,\mbox{s}^{-1}$，不稳定性增长时间为1分钟。因此，过渡区可能会受到这种快速增长的回转粘性不稳定性的影响。

英文摘要：

The dynamics of the partially ionized solar atmosphere is controlled by the frequent collision and charge exchange between the predominant neutral Hydrogen atoms and charged ions. At signal frequencies below or of the order of either of the collision or charge exchange frequencies the magnetic stress is {\it felt} by both the charged and neutral particles simultaneously. The resulting neutral-mass loading of the ions leads to the rescaling of the effective ion-cyclotron frequency-it becomes the Hall frequency, and the resultant effective Larmor radius becomes of the order of few kms. Thus the finite Larmor radius (FLR) effect which manifests as the ion and neutral pressure stress tensors operates over macroscopic scales. Whereas parallel and perpendicular (with respect to the magnetic field) viscous momentum transport competes with the Ohm and Hall diffusion of the magnetic field in the photosphere-chromosphre, the gyroviscous effect becomes important only in the transition region between the chromosphere and corona, where it competes with the ambipolar diffusion. The wave propagation in the gyroviscous effect dominated medium depends on the plasma $β$ (a ratio of the thermal and magnetic energies). The abundance of free energy makes gyro waves unstable with the onset condition exactly opposite of the Hall instability. However, the maximum growth rate is identical to the Hall instability. For a flow gradient $\sim 0.1 \,\mbox{s}^{-1}$ the instability growth time is one minute. Thus, the transition region may become subject to this fast growing, gyroviscous instability.

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