标题： 太阳电流片中的三维耦合撕裂-热演化 显示英文标题

标题： 3D coupled tearing-thermal evolution in solar current sheets

摘要： 电流片的撕裂-热演化共同作用在太阳大气中电流片的破裂以及冷凝结构的形成中起着重要作用。然而，迄今为止这一现象并未得到充分关注。 我们通过数值模拟研究了太阳大气中一种结合了撕裂和热不稳定性因素的机制，该机制导致理想化电流片的分裂。热效应在三维磁重联拓扑结构中形成了局部冷却的冷凝结构。 我们在基于开源代码MPI-AMRVAC的太阳大气条件下构建了一个力自由电流片的三维电阻磁流体力学模拟，此模拟考虑了背景加热的非绝热影响、光学薄辐射能量损失以及磁场方向上的热传导。 多级自适应网格细化揭示了系统演化过程中更精细尺度冷凝结构的一致性发展。电流片中的不稳定性由集中在电流片平面附近的磁场扰动触发，并随后发展出撕裂模式。这又引发了与系统热不稳定性相关的热失控现象。 我们发现，在当前低等离子体-条件（$\beta$）下形成的后续局部冷却等离子体冷凝结构，并证明这些冷凝结构的密度和温度与更安静的日冕冷凝结构相似。 极端紫外（EUV）和光学波段的合成对应物显示了等离子体团（在EUV中）、以及类似于日冕冷凝物和日冕雨滴的重连区域附近冷凝结构的形成。 我们的模拟表明，太阳电流片中的三维重联可能不可避免地表现出多温特性，这种特性是在它们的耦合撕裂-热演化过程中形成的。 显示英文摘要

摘要： Combined tearing-thermal evolution plays an important role in the disruption of current sheets, and formation of cool condensations within the solar atmosphere. However, this has received limited attention to date. We numerically explore a combined tearing and thermal instability that causes the break up of an idealized current sheet in the solar atmosphere. The thermal component leads to the formation of localized, cool condensations within an otherwise 3D reconnecting magnetic topology. We construct a 3D resistive magnetohydrodynamic simulation of a force-free current sheet under solar atmospheric conditions that incorporate the non-adiabatic influence of background heating, optically thin radiative energy loss, and magnetic field aligned thermal conduction with the open source code MPI-AMRVAC. Multiple levels of adaptive mesh refinement reveal the self-consistent development of finer-scale condensation structures within the evolving system. The instability in the current sheet is triggered by magnetic field perturbations concentrated around the current sheet plane, and subsequent tearing modes develop. This in turn drives thermal runaway associated with the thermal instability of the system. We find subsequent, localized cool plasma condensations that form under the prevailing low plasma-$\beta$ conditions, and demonstrate that the density and temperature of these condensed structures are similar to more quiescent coronal condensations. Synthetic counterparts at Extreme-UltraViolet (EUV) and optical wavelengths show the formation of plasmoids (in EUV), and coronal condensations similar to prominences and coronal rain blobs in the vicinity of the reconnecting sheet. Our simulations imply that 3D reconnection in solar current sheets may well present an almost unavoidable multi-thermal aspect, that forms during their coupled tearing-thermal evolution.