Competition Between Coalescence and Three‐Dimensional Instabilities

Many different nonlinear processes can occur in current sheets following the development of magnetic islands. Two of the most important are the coalescence instability and the secondary, or three‐dimensional, instability. In this paper we describe the results of some numerical expriments in which both instabilities are present, in an effort to determine which instability will be dominant. It is our finding that, for a wide variety of initial conditions and parameters, that the secondary instability grows a a faster rate than the coalescence instability.