3D Magnetic Reconnection in SSX: Dedalus Simulation

We present the results of simulations of magnetic reconnection in the Swarthmore Spheromak Experiment (SSX). We use Dedalus, an open-source flexible spectral method Python framework, to simulate MHD time evolution of two spheromaks merging in a cylindrical 1:10 chamber. We use CFL dynamic timestepping in a 64x64x320 resolution Cartesian grid, with periodic boundary conditions. Magnetized plasma guns fire plasma plumes towards each other in a meter long flux conserver, relaxing before merging at the midplane and resistively dissipating, all over the course of ~100 Alfvén times. To replicate these conditions, we start our simulation with a density distribution of two spheromaks at opposite ends of the z-dimension of the grid, and give both spheromaks initial z-velocity towards each other. Temperature is initialized proportionally to density under ideal gas assumptions. Typical magnetic Reynolds number Rm ≈ 1000 and mechanical Reynolds number Re ≈ 200. The vector potential is initialized from the force-free equation ∇ × B = λB and given a perturbation to break axial symmetry. The simulation runs for ~20 Alfvén times during the reconnection event, with the spheromaks merging in the midplane at ~5 Alfvén times.