Self-organization during spherical torus formation by flux rope merging in the Mega Ampere Spherical Tokamak

Abstract

Merging-compression start-up in the Mega Ampere Spherical Tokamak provides an opportunity to investigate the merging of flux ropes through magnetic reconnection, and the self-organization into a single flux rope, in a low-plasma-β, high-Lundquist-number plasma. We present an overview of simulations of this process using the compressible Hall-MHD equations in two dimensions. Preliminary results of an analytical model of the self-organization, assuming a helicity-conserving relaxation to a minimum energy state, are also presented. The relevance of these models to solar plasmas is discussed.