Effects of compressibility on the finite Larmor radius stabilized Rayleigh-Taylor instability in Z-pinch implosions

The effects of compressibility on the Rayleigh-Taylor (RT) instability in a. finite Larmor radius (FLR) plasma of magnetic field acceleration are studied by means of FLR magnetohydrodynamic (MHD) theory. FLR effects are introduced in the momentum equation of MHD theory through an anisotropic ion stress tensor. The linear mode equation which includes main equilibrium quantities and their high-order differential terms is derived. The dispersion equation is solved numerically. The main results indicate that in the compressible FLR plasma the growth rate of the RT instability displays faster growing and broader wavenumber range; and a new branch of low-frequency and long-wavelength instability, whose real frequency is positive (opposite from the negative real frequency of the RT instability), is found in the compressible FLR plasma. That is, plasma compressibility is a destabilizing factor for both the FLR stabilized RT instability and the new branch of instability. (c) 2008 American Institute of Physics.