On the application of numerical continuation methods to the calculation of magnetostatic equilibria

Sequences of magnetostatic equilibria can often be used to model the quasi-static pre-eruptive energy storage phase of eruptive phenomena in e.g. Earth's magnetosphere or the solar corona. During these phases the systems evolve only due to slow changes in their environment, being practically in equilibrium on large scales. The eruption onset would then be identified with a bifurcation or catastrophe point in the solution diagram. Different energy storage mechanisms can be studied by different parameterizations of e.g. the boundary conditions. Also from the more fundamental point-of-view of the theory of dynamical systems, studying the possible stationary states and the bifurcation properties of plasma systems should be the first step towards a more thorough understanding of their full dynamical behaviour. In any case one will have to solve highly non-linear partial differential equations with the possibility of the existence of multiple solutions (or of none at all) for a given set of boundary conditions. Such problems can, in general, only be solved numerically. The most appropriate class of numerical algorithms for this type of problem are continuation methods which can calculate complete solution branches and detect bifurcation points. In this work a numerical bifurcation code based on a continuation method is presented. In addition to solving the non-linear magnetohydrostatic equations, the code can check a sufficient linear stability criterion for each solution. Some preliminary results for simple magnetohydrostatic equilibria are presented and potential future applications are discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.