The Rayleigh-Taylor instability of a compressible plasma in the presence of a horizontal magnetic field is investigated, taking into account the effects of finite Larmor radius. Only transverse perturbations are considered. The problem is shown to be characterized by a variational principle. Using it, the dispersion relation is obtained for a plasma layer of finite thickness and having an exponentially varying density. It is found that the finite Larmor radius effects can thoroughly stabilize unstable configurations. For configurations which are not completely stabilized, the compressibility stabilizes some of the disturbances which are unstable for an incompressible plasma. © 1993, Walter de Gruyter. All rights reserved.
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