Fast magnetic reconnection plays a fundamental role in driving explosive dynamics and heating in the solar chromosphere. The reconnection time scale of traditional models is shortened at the onset of the coalescence instability, which forms a turbulent reconnecting current sheet through plasmoid interaction. In this work, we aim to investigate the role of partial ionization in the development of fast reconnection through the study of the coalescence instability of plasmoids. Unlike the processes occurring in fully ionized coronal plasmas, relatively little is known about how fast reconnection develops in partially ionized plasmas (PIPs) of the chromosphere. We present 2.5D numerical simulations of coalescing plasmoids in a single fluid magnetohydrodynamic (MHD) model and a two-fluid model of a partially ionized plasma (PIP). We find that in the PIP model, which has the same total density as the MHD model but an initial plasma density two orders of magnitude smaller, plasmoid coalescence is faster than the MHD case, following the faster thinning of the current sheet and secondary plasmoid dynamics. Secondary plasmoids form in the PIP model where the effective Lundquist number $S=7.8\times {10}^3$, but are absent from the MHD case where $S=9.7\times {10}^3$: these are responsible for a more violent reconnection. Secondary plasmoids also form in linearly stable conditions as a consequence of the nonlinear dynamics of the neutrals in the inflow. In the light of these results, we can affirm that two-fluid effects play a major role in the processes occurring in the solar chromosphere.

中文翻译：

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色球部分电离等离子体中的聚结不稳定性

快速磁重新连接在驱动太阳色球中的爆炸动力学和加热方面起着基本作用。在聚结不稳定性开始时，传统模型的重新连接时间尺度缩短了，这通过等离子体相互作用形成了湍流的重新连接电流层。在这项工作中，我们旨在通过研究等离子体的聚结不稳定性来研究部分电离在快速重新连接发展中的作用。与完全电离的冠状等离子体中发生的过程不同，关于在色球的部分电离的等离子体（PIP）中如何快速重新建立连接的了解相对较少。我们目前在单个流体磁流体动力学（MHD）模型和部分电离等离子体（PIP）的两个流体模型中凝聚等离子体的2.5D数值模拟。我们发现，在PIP模型中，其总密度与MHD模型相同，但初始等离子体密度小两个数量级，因此随着当前薄层和第二次等离子体动力学的变薄，等离子体融合比MHD情况要快。 。在有效Lundquist数所在的PIP模型中形成次质浆$\mathrm{小号}=7.8\times {10}^3$，但在MHD案例中却没有 $\mathrm{小号}=9.7\times {10}^3$：这些负责更剧烈的重新连接。由于流入中性点的非线性动力学，次级等离子体也会在线性稳定的条件下形成。根据这些结果，我们可以确定两种流体效应在太阳色球层中发生的过程中起着重要作用。