KELVIN-HELMHOLTZ INSTABILITIES IN RADIATING FLOWS

The linear Kelvin-Helmholtz stability regime of two radiating fluids in relative motion is discussed. The study is carried out in plane geometry and in the vortex-sheet approximation. Attention is focused on the effects of radiation losses on the instability pattern: it is found that the principal effect is the suppression of the cutoff at Mach number M = 2 square-root 2, typical of the adiabatic Kelvin-Helmholtz mode; in particular radiation effects are small on the instability below the cutoff, while they become dominant above. Radiating fluids are also typically affected by thermal instability. In fact thermal modes are found also in the present case: they may have growth rates comparable to the Kelvin-Helmholtz instability above the cutoff.