Zonal and streamer structures in magnetic-curvature-driven Rayleigh-Taylorinstability

A detailed numerical investigation of the nonlinear evolution of the magnet ic curvature-driven Rayleigh-Taylor instability is carried out. The evoluti on is found to follow one of two distinct paths-that leading to a saturated zonal flow pattern or growing streamer structures. For a fixed value of th e density gradient and the magnetic field gradient, the parametric regimes for the occurrence of these two states is delineated in the form of a phase diagram in the D-mu space, where D is the diffusion coefficient and mu is the viscosity parameter. The bifurcation behavior is explained on the basis of a reduced quasilinear model and the final saturated state of zonal flow s is understood from a phenomenological zero-dimensional model. (C) 2001 Am erican Institute of Physics.