Rayleigh-Taylor Instabilities in a Dilute Plasma

Daniel Lecoanet

April 16, 2012

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Abstract: There are many astrophysical examples of density discontinuities across an interface, while the pressure remains continuous, ranging from cold fronts in galaxy clusters to emerging magnetic flux in the solar corona. These contact discontinuities can be unstable to the Rayleigh-Taylor instability if the density gradient is opposite the direction of gravity. In some contexts, the plasma near a contact discontinuity is hot and dilute, which causes heat conduction to be anisotropic along magnetic field lines. In this talk, I will discuss how anisotropic heat conduction alters the Rayleigh-Taylor instability, both in the linear and nonlinear regimes. Numerical simulations suggest that the nonlinear evolution can be described as the superposition of three physical processes: vertical temperature diffusion; motion of Rayleigh-Taylor bubbles and spikes; and the heat flux driven buoyancy instability.