Oscillatory reconnection and waves driven by merging magnetic flux ropes in solar flares
Oscillatory reconnection and waves driven by merging magnetic flux ropes in solar flares
复制标题
太阳耀斑中合并磁通绳驱动的振荡重联和波
DOI：
10.1093/mnras/stac1286
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发表时间：
2022
影响因子：
4.8
通讯作者：
Stewart J
中科院分区：
文献类型：
--
作者：
Stewart J
振荡重联是一个被认为是太阳和恒星现象的基础的过程，并且可能在耀斑等瞬变事件中发挥重要作用。耀斑辐射中的准周期脉动可能是振荡重联的一种表现，但其内在机制仍不确定。在本文中，我们提出了二维磁流体动力学模拟的两个载流磁通绳与面外磁场进行振荡重联，其中两个磁通绳合并成一个单一的磁通绳。我们发现，振荡重联可以发生本质上没有外部振荡驱动器的磁通绳聚结过程中，这可能会发生在大规模的日冕环相互作用和合并的等离子体团在破碎的电流片。此外，我们表明，径向传播的非线性波产生的磁通绳合并后，由于合并磁通绳的后重联振荡。这些波的行为被发现是几乎独立的初始面外磁场。据估计，通过合并日冕环和环顶电流片中合并等离子体团发射的波的典型相速度分别为90和900 km s-1。这是可能的，在磁绳聚结过程中发射的波的属性可以被用作诊断工具，以确定在聚结区域内的物理参数。
Oscillatory reconnection is a process that has been suggested to underlie several solar and stellar phenomena, and is likely to play an important role in transient events such as flares. Quasi-periodic pulsations in flare emissions may be a manifestation of oscillatory reconnection, but the underlying mechanisms remain uncertain. In this paper, we present 2D magnetohydrodynamic simulations of two current-carrying magnetic flux ropes with an out-of-plane magnetic field undergoing oscillatory reconnection in which the two flux ropes merge into a single flux rope. We find that oscillatory reconnection can occur intrinsically without an external oscillatory driver during flux rope coalescence, which may occur both during large-scale coronal loop interactions and the merging of plasmoids in fragmented current sheets. Furthermore, we demonstrate that radially propagating non-linear waves are produced in the aftermath of flux rope coalescence, due to the post-reconnection oscillations of the merged flux rope. The behaviour of these waves is found to be almost independent of the initial out-of-plane magnetic field. It is estimated that the waves emitted through merging coronal loops and merging plasmoids in loop-top current sheets would have a typical phase speed of 90 and 900 km s−1, respectively. It is possible that the properties of the waves emitted during flux rope coalescence could be used as a diagnostic tool to determine physical parameters within a coalescing region.