Title: The coupled tearing-thermal instability in coronal current sheets from the linear to the non-linear stage Show Chinese title

Title: 日冕电流片中从线性阶段到非线性阶段的耦合撕裂-热不稳定性

Abstract: In the solar corona, magnetically sheared structures are unstable to both tearing and thermal instabilities in a coupled fashion. However, how the choice of linear perturbation modes influences the time-scale to achieve the thermal runaway in a coupled tearing-thermal coronal current sheet is not well understood to date. Here, we model a force-free Harris current sheet under solar coronal conditions to investigate this coupling in the linear and non-linear regimes. In the linear regime, we adopt the magnetohydrodynamic spectroscopy code Legolas to compare the current sheet under thermal and thermoresistive conditions, after which we initialise non-linear simulations (with MPI-AMRVAC) with the unstable, linear tearing and thermal perturbations obtained with Legolas. It is shown that part of the unstable thermal quasi-continuum adopts tearing properties in the linear stage, but that it is not until the non-linear stage is reached that a true thermal 'runaway' effect leads to condensations inside tearing-induced flux ropes. Hence, the linear stage is governed by the dominant tearing instability whilst condensations form due to tearing-thermal coupling in the non-linear stage. Our results imply that perturbing an equilibrium current sheet with the fastest growing linear mode skips the mode mixing phase in which the dominant instability traditionally emerges, and significantly reduces the time-scale to enter into the non-linear stage and thermal runaway process from its equilibrium configuration. Show Chinese abstract

Abstract: 在太阳日冕中，磁化剪切结构在耦合的情况下不稳定，既可能受到撕裂不稳定性的影响，也可能受到热不稳定性的影响。然而，到目前为止，人们还不清楚线性扰动模态的选择如何影响耦合撕裂-热日冕电流片达到热失控的时间尺度。在这里，我们模拟了太阳日冕条件下的力自由哈里斯电流片，以研究这种耦合在线性和非线性范围内的表现。在线性范围内，我们采用磁流体力学光谱代码Legolas来比较热和热阻条件下的电流片，之后用MPI-AMRVAC初始化非线性模拟，使用通过Legolas获得的不稳定的线性撕裂和热扰动。结果显示，部分不稳定的热准连续谱在初始阶段表现出撕裂特性，但直到非线性阶段才出现真正的热“失控”效应，在由撕裂诱导的磁通绳内形成冷凝物。因此，线性阶段受主导的撕裂不稳定性控制，而冷凝物则由于撕裂-热耦合作用在非线性阶段形成。我们的结果表明，用最快增长的线性模式扰动一个平衡电流片可以跳过传统上主要不稳定性出现的模式混合阶段，并显著减少从平衡配置进入非线性阶段和热失控过程的时间尺度。