Influence of heating rate on the condensational instability

Abstract

We determine by analysis and numerical simulation the effect that various heating rates have on the linear and nonlinear evolution of a typical plasma within a solar magnetic flux tube subject to the condensational instability. We first derive a dispersion relation for infinitesimal disturbances to a condensationally unstable fluid subject to heating rates which are functions of temperature and thermal pressure. This relation leads to an algebraic model for predicting solar flux tube stability in the longwavelength limit as a function of temperature. We find that linear stability depends strongly on the heating rate. We then present the results of numerical simulations of the nonlinear evolution of the condensational instability in a solar magnetic flux tube. Different heating rates lead to quite different nonlinear evolution, as evidenced by the behaviour of the global internal energy. Almost all of the heating rates that we consider produce saturation in bifurcated states, but at somewhat different temperatures and mass densities.