The roles of advection and diffusion in planar magnetic merging solutions

Abstract

Since cosmic plasmas are highly conducting, large-scale magnetic fields are tied almost completely to the velocity field of the fluid. Only in localized regions of strong current density can the magnetic field slip through the plasma, allowing magnetic energy to be converted into ohmic heating or the kinetic energy of mass motion. Here we contrast the roles of advection and resistive diffusion in three different steady-state two-dimensional models for magnetic energy conversion: magnetic annihilation, reconnective diffusion and a kinematic model based on the classical magnetic reconnection picture. First we examine the diagnostic of ‘field-line slippage’ and show that it provides a useful indicator of the relative importance of advection and diffusion in each solution. We then quantify the energy release characteristics of the different models by examining the ratio of ohmic heat to kinetic energy generation.