Starting from an exact, steady-state, force-free solution of themagnetohydrodynamic (MHD) equations, we investigate how resistive currentlayers are induced by perturbing line-tied three-dimensional magneticequilibria. This is achieved by the superposition of a weak perturbation fieldin the domain, in contrast to studies where the boundary is driven by slowmotions, like those present in photospheric active regions. Our aim is toquantify how the current structures are altered by the contribution of socalled quasi-separatrix layers (QSLs) as the null point is shifted outside thecomputational domain. Previous studies based on magneto-frictional relaxationhave indicated that, despite the severe field line gradients of the QSL, thepresence of a null is vital in maintaining fast reconnection. Here, we explorethis notion using highly resolved simulations of the full MHD evolution. Weshow that for the null-point configuration, the resistive scaling of the peakcurrent density is close to $J\sim\eta^{-1}$, while the scaling is much weaker,i.e. $J\sim\eta^{-0.4}$, when only the QSL connectivity gradients provide asite for the current accumulation.
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机译：从他们的磁流体动力学（MHD）方程的精确，稳态，无力解开始，我们研究了如何通过扰动束缚的三维磁平衡来感应电阻电流层。这是通过在域中叠加一个微弱的扰动场来实现的，这与边界受慢动作驱动的研究（如存在于光球活动区域中的那些）的研究形成了鲜明的对比。我们的目的是量化当零点移出计算域之外时，如何通过所谓的准分离层（QSL）的贡献来改变当前结构。先前基于磁摩擦弛豫的研究表明，尽管QSL出现了严重的磁力线梯度，但零位的存在对于维持快速重新连接至关重要。在这里，我们使用高度解析的完整MHD演变模拟来探索这一概念。我们显示，对于零点配置，峰值电流密度的电阻缩放接近$ J \ sim \ eta ^ {-1} $，而缩放则弱得多，即$ J \ sim \ eta ^ {-0.4} $，仅当QSL连接梯度为当前累积提供位置时。
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