Stability of a cosmic ray modified tangential discontinuity

Abstract

We consider the dispersion relation for waves in a cosmic ray modified plasma for the case when the background flow consists of a cosmic ray pressure balance structure, in which pg+pc=const. where pc and pg denote the cosmic ray and thermal gas pressures respectively. The stability analysis shows that waves at an arbitrary point in the flow may be driven unstable if the cosmic ray pressure gradient is sufficiently large to overcome wave damping due to cosmic ray diffusion. Following S. Chalov’s work (1) we analyze the instability of a cosmic ray modified tangential discontinuity. Chalov considered the case where pc=const. throughout the structure, whereas in our analysis both pc and pg vary in the direction perpendicular to the surface separating two flow regions. Predictions of the linear theory are compared to numerical simulations. Applications to the stability of the heliopause are discussed.