ONE-DIMENSIONAL MERGING OF MAGNETIC-FIELDS WITH COOLING

A correct understanding of the process of magnetic reconnection is ver y important for the proper understanding of many astrophysical situati ons in which magnetic fields are involved. The main element in magneti c reconnection is the existence of a very thin layer over which the ma gnetic field reverses. In order to understand how such a layer forms s pontaneously, we consider an initial one dimensional equilibrium with magnetic field going linearly through zero. Then we assume that plasma starts to cool at a rate proportional to pressure. This throws the si tuation out of equilibrium, and adiabatic compression commences in ord er to keep the situation in equilibrium. This leads quickly to a narro w layer across which the magnetic field reverses, and in which the res istivity destroys the magnetic field. We are able to analyze the resis tive evolution analytically by a boundary layer analysis. It turns out that the layer forms in a cooling time multiplied by the logarithm of the magnetic Reynolds number. After the layer forms all the magnetic flux is destroyed in a few more cooling times.