Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. Recent laboratory experiments designed to study these eruptive instabilities have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528, 526) and quasi-static (Myers et al 2016 Phys. Plasmas, in press) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In this paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. While the quasi-static tension force is found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.

太阳爆发活动通常由作用于线束缚磁通量绳（line-tied magnetic flux ropes）的磁流体动力学不稳定性（magnetohydrodynamic instabilities）驱动，此类不稳定性包括环不稳定性与扭缠不稳定性。近期为研究此类爆发性不稳定性而开展的实验室实验证实，动态磁张力与准静态磁张力均对线束缚磁通量绳的平衡与稳定性起到关键作用（Myers等，2015，《自然》，528卷，526页；Myers等，2016，《等离子体物理》，待刊）。本文整合上述实验室研究成果，并探究动态与准静态磁张力之间的关联机制。尽管准静态磁张力在多种工况下均可助力磁通量绳的平衡，但动态磁张力的显著作用主要集中于所谓的“失效环态”区间——在此区间内，磁自组织事件会阻碍磁通量绳爆发。