MHD simulation of coalescence process of spheromaks

We have studied merging processes of two spheromaks by means of a two-dimensional MHD (magnetohydrodynamics) simulation. In counter-helicity merging where the two spheromaks have anti-parallel magnetic helicity, an FRC (field-reversed configuration) is realized after the coalescence of the low-β spheromaks, while a larger spheromak (or a prolomak) is formed in a co-helicity case. Magnetic reconnection driven by attracting motion of spheromaks plays a key role in energy transfer, topological change of field lines, and acceleration of toroidal and poloidal flows. The results obtained here are in good agreement with the TS-3 experiments. It should be emphasized that pressure structure in the FRC is spontaneously generated by thermal transport due to the poloidal flow, and that the final state satisfies the force-balanced condition of jxB=∇p. (author)