  Three-dimensional (3D) magnetohydrodynamic simulations are carried out to
explore magnetic reconnections in the presence of 3D magnetic nulls and
quasi-separatrix layers (QSLs). The initial magnetic fields are created by
superposing uniform vertical magnetic fields of two different magnitudes on a
linear force-free field. The interior of the numerical box contains two 3D
nulls with separatrix domes separated by a quasi-separator (or hyperbolic flux
tube) with QSLs. In the first simulation, the uniform vertical field is so
large that the nulls are located at low heights and the domes are separate.
Initially unbalanced Lorentz forces drive rotational flows that form strong
electric currents and strong torsional fan reconnection at the 3D nulls and
weak QSL reconnection at the hyperbolic flux tube. Flipping or slipping of
field lines is observed in both cases. In the second simulation, with a weaker
vertical field and larger domes, the separatrix surfaces meet at the central
quasi-separator and their rotation drives stronger QSL reconnection than
before.
