The aim of this paper is to give a result concerning the stability properties
of the solutions of magnetohydrodynamics equations at small but finite Reynolds
numbers. These solutions are found using the alpha-effect: this method gives us
solutions which are highly oscillating spatially on the scale of the underlying
flow but are growing on a larger scale depending on a parameter epsilon. We
prove nonlinear stability and instability results for a dense subset of initial
velocity field of the flow at given Reynolds number.Comment: 14 page