The Spontaneous Formation of Current-Sheets in Astrophysical Magnetic Fields

Abstract

This article is an introduction to Parker's idea that electric current sheets form spontaneously in astrophysical magnetic fields under the condition of high electrical conductivity. Upon formation, the current sheets will collapse to such small widths as to result in resistive reconnection of magnetic fields and heating, despite the very large but finite electrical conductivity. This mechanism is an attractive explanation of the ubiquitous association between magnetic fields and heated plasmas in many astrophysical situations. The hydromagnetic process of this mechanism is illustrated, using a well-studied two-dimensional Cartesian model involving a quadrupolar magnetic field with or without a magnetic null point. The purpose of this illustration is to acquaint the reader with the basic physics in terms of elementary mathematical results and familiar properties which are possible to obtain for this simple model. The general and more complicated processes in three-dimensional magnetic fields is treated in Parker's latest (1994) monograph on this subject.