NONLINEAR COMPRESSIBLE MAGNETOCONVECTION .2. STREAMING INSTABILITIES IN 2 DIMENSIONS

We have conducted further numerical experiments on two-dimensional ful ly compressible convection in an imposed vertical magnetic held and in terpreted the results by reference to appropriate low-order models. He re we focus on streaming instabilities, involving horizontal shear flo ws, which form an important mechanism for the breakdown of steady conv ection in relatively weak fields for boxes of sufficiently small aspec t ratio. While these shearing modes can arise even in the absence of a field, they will typically lead only to travelling and modulated wave s unless there is a field to provide a restoring force. For magnetocon vection a new and dramatic form of pulsating wave appears after a comp lex sequence of secondary bifurcations.