A relaxation model of coronal heating in multiple interacting flux ropes
A relaxation model of coronal heating in multiple interacting flux ropes
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DOI：
10.1051/0004-6361/201629589
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发表时间：
2017-04-01
影响因子：
6.5
通讯作者：
Hood, A. W.
中科院分区：
文献类型：
--
作者：
Hussain, A. S.;Browning, P. K.;Hood, A. W.
语境。加热日冕需要耗散储存的磁能，这可能发生在扭曲的磁场中。最近发表的数值模拟表明，扭曲磁力线中理想的扭结不稳定性可能会触发稳定的扭曲邻居的能量释放，并展示大量的加热事件。我们的目标是构建两个磁绳能量释放的泰勒松弛模型，并将其与模拟结果进行比较。然后，我们的目标是将模型扩展到大量的磁通绳，从而可以对热雪崩进行建模，并计算具有不同捻度轮廓的捻线集合的能量释放。方法。最终状态是通过假设螺旋度守恒弛豫到最小能量状态来计算的。研究了多种情况，包括扭结不稳定的磁通绳自行松弛，以及稳定和不稳定的磁通绳由于磁重联而合并成单根绳。我们考虑确定最终松弛状态的空间范围的替代约束。结果。对于两个扭曲线的相互作用和多线雪崩，松弛模型和磁流体动力学模拟之间存在良好的一致性。该模型可以预测不同扭曲程度的磁绳的能量释放，这些磁绳单独松弛或通过重新连接合并成单个磁绳。结果发现，合并磁通绳的能量输出主要由最强力扭绞绳的能量决定。结论。弛豫方法可以很好地估计扭结不稳定的扭结线集合中的能量释放。
Context. Heating the solar corona requires dissipation of stored magnetic energy, which may occur in twisted magnetic fields. Recently published numerical simulations show that the ideal kink instability in a twisted magnetic thread may trigger energy release in stable twisted neighbours, and demonstrate an avalanche of heating events.Aims. We aim to construct a Taylor relaxation model for the energy release from two flux ropes and compare this with the outcomes of the simulations. We then aim to extend the model to large numbers of flux ropes, allowing the possibility of modelling a heating avalanche, and calculation of the energy release for ensembles of twisted threads with varying twist profiles.Methods. The final state is calculated by assuming a helicity-conserving relaxation to a minimum energy state. Multiple scenarios are examined, which include kink-unstable flux ropes relaxing on their own, as well as stable and unstable flux ropes merging into a single rope as a result of magnetic reconnection. We consider alternative constraints that determine the spatial extent of the final relaxed state.Results. Good agreement is found between the relaxation model and the magnetohydrodynamic simulations, both for interactions of two twisted threads and for a multi-thread avalanche. The model can predict the energy release for flux ropes of varying degrees of twist, which relax individually or which merge through reconnection into a single flux rope. It is found that the energy output of merging flux ropes is dominated by the energy of the most strongly twisted rope.Conclusions. The relaxation approach provides a very good estimate of the energy release in an ensemble of twisted threads of which one is kink-unstable.