ACOUSTIC-EMISSION AND COROTATIONAL INSTABILITY OF SHOCKS MODIFIED BY STRONG PARTICLE-ACCELERATION

The effect of particles that undergo strong diffusive-shock-accelerati on on the stability of the accelerating shock is investigated. A two-f luid model is employed in which the accelerated particles are treated as a fluid whose effect is incorporated as an additional pressure in t he momentum equation. The Dyakov and Kontorovich stability criteria ar e used in order to study the stability of those steady-state shocks th at contain a gas sub-shock. The downstream conditions of the latter ar e parametrized by the ratio of the upstream acclerated-particles press ure to the total pressure. For some range of values of that parameter, three possible downstream states are possible for each upstream state . It is shown that in that range of parameters the shocks are either c orrugationally unstable or lose their energy by spontaneous emission o f acoustic as well as entropy-vortex waves.