arXiv 1601.020442016-01-08astro-ph.SR

三维磁并合的模拟：电阻标度法研究磁并合点和QSL重联

Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection

Frederic Effenberger, I. J. D. Craig

备注：: 13 pages, 4 figures, The final publication is available at Springer via http://dx.doi.org/10.1007/s11207-015-0825-6
发表信息：: Solar Physics, 291(1), 143-153, Jan 2016
DOI：: 10.1007/s11207-015-0825-6

摘要：

从一个精确的，稳态的，无力的解决方案的磁流体动力学（MHD）方程，我们调查如何电阻电流层引起的扰动线束缚的三维磁平衡。这是通过在域中叠加弱扰动场来实现的，与边界由慢运动驱动的研究相反，如光球活动区中存在的那些。我们的目标是量化的电流结构是如何改变的贡献，所谓的准分界线层（QSL）的零点被转移到计算域之外。先前基于磁摩擦弛豫的研究表明，尽管QSL存在严重的磁力线梯度，但零的存在对于维持快速重联至关重要。在这里，我们探索这个概念，使用高分辨率的模拟完整的MHD的演变。我们发现，对于零点配置，峰值电流密度的电阻缩放接近$J\simη^{-1}$，而缩放要弱得多，即$J\simη^{-0.4}$，当只有QSL连接梯度提供一个网站的电流积累。

英文摘要：

Starting from an exact, steady-state, force-free solution of the magnetohydrodynamic (MHD) equations, we investigate how resistive current layers are induced by perturbing line-tied three-dimensional magnetic equilibria. This is achieved by the superposition of a weak perturbation field in the domain, in contrast to studies where the boundary is driven by slow motions, like those present in photospheric active regions. Our aim is to quantify how the current structures are altered by the contribution of so called quasi-separatrix layers (QSLs) as the null point is shifted outside the computational domain. Previous studies based on magneto-frictional relaxation have indicated that, despite the severe field line gradients of the QSL, the presence of a null is vital in maintaining fast reconnection. Here, we explore this notion using highly resolved simulations of the full MHD evolution. We show that for the null-point configuration, the resistive scaling of the peak current density is close to $J\simη^{-1}$, while the scaling is much weaker, i.e. $J\simη^{-0.4}$, when only the QSL connectivity gradients provide a site for the current accumulation.

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