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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.

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