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arXiv 2409.06901astro-ph.SRphysics.plasm-ph
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部分电离等离子体中磁通量绳的扭结不稳定性

Kink instability of flux ropes in partially-ionised plasmas

Giulia Murtas, Andrew Hillier, Ben Snow

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17 pages, 10 figures. Accepted by ApJ
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AI总结：

该研究针对部分电离等离子体中的磁通量绳扭结不稳定性展开，发现部分电离会加快不稳定性非线性阶段起始、提升内能增幅与升温速率，使色球磁通量绳动力学更具爆发性，为理解微暗条喷发等小尺度色球结构的作用提供关键依据。

摘要：

在太阳大气中，磁通量绳会受到电流驱动的不稳定性作用，这类不稳定性对等离子体喷发、抛射和加热过程至关重要。磁通量绳中发展的一种典型理想磁流体力学（MHD）不稳定性是螺旋扭结不稳定性，它会使磁通量绳的轴发生扭曲。这种不稳定性的增长可触发磁重联，这能够解释色球喷流和针状体的形成，但此前从未在部分电离等离子体（PIP）中研究过它的发展过程。本文研究了部分电离等离子体中的扭结不稳定性，以了解其在受电荷-中性粒子相互作用影响的太阳色球中的发展机制。部分电离会加快不稳定性非线性阶段的起始，因为孤立等离子体的等离子体β小于整体等离子体的总等离子体β。完全电离等离子体与部分电离等离子体中释放的磁能分布存在差异，部分电离等离子体情形下的内能增幅更大。部分电离等离子体中的温度上升更快，这也源于双流体动力学的加热项。部分电离等离子体效应会在更短的时间尺度上触发扭结不稳定性，这体现为色球磁通量绳的动力学过程更具爆发性。这些结果对于理解小尺度色球结构——微暗条喷发——的动力学至关重要，这类结构此前在很大程度上被忽视，但可能对色球加热和喷流形成有显著贡献。

英文摘要：

In the solar atmosphere, flux ropes are subject to current driven instabilities that are crucial in driving plasma eruptions, ejections and heating. A typical ideal magnetohydrodynamics (MHD) instability developing in flux ropes is the helical kink, which twists the flux rope axis. The growth of this instability can trigger magnetic reconnection, which can explain the formation of chromospheric jets and spicules, but its development has never been investigated in a partially-ionised plasma (PIP). Here we study the kink instability in PIP to understand how it develops in the solar chromosphere, where it is affected by charge-neutral interactions. Partial ionisation speeds up the onset of the non-linear phase of the instability, as the plasma $β$ of the isolated plasma is smaller than the total plasma $β$ of the bulk. The distribution of the released magnetic energy changes in fully and partially-ionised plasmas, with a larger increase of internal energy associated to the PIP cases. The temperature in PIP increases faster also due to heating terms from the two-fluid dynamics. PIP effects trigger the kink instability on shorter time scales, which is reflected in a more explosive chromospheric flux rope dynamics. These results are crucial to understand the dynamics of small-scale chromospheric structures - mini-filament eruptions - that this far have been largely neglected but could significantly contribute to chromospheric heating and jet formation.

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