Dynamic and gravitational instabilities of spherical shocks
In this paper we examine the stability of a thin spherical shock against dynamic and gravitational perturbations when the wavelength of the perturbation is large compared to the thickness of the dense shell. For dynamic perturbations, we find that a spherical isothermal shock, driven by a hot gas, is overstable against small perturbations. As a result, the fragmentation of the shell proceeds in an oscillatory manner. The smaller wavelength perturbations are most unstable, with the maximum growth rate being comparable to the inverse of the time it takes sound waves to propagate through the shell thickness. The nonradiating case is not subject to this overstability unless d ln P/d in rho is close to 1. The overstability can appear in cases where there is an ambient magnetic field. We also consider the growth of gravitationally driven perturbations. On cosmological time scales all such shocks are unstable, with the density perturbations growing as power laws in time. In the nonradiating case the maximum exponent is close to 1. On shorter time scales, only the isothermal shocks are unstable. Whenever the overstability mechanism is at work, gravitational instabilities can be neglected. We discuss the implications of these results for star formation, and for hydrodynamic galaxy formation.
- Research Organization:
- Princeton University Observatory
- OSTI ID:
- 6860923
- Journal Information:
- Astrophys. J.; (United States), Vol. 274:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
NUMERICAL STUDY OF THE VISHNIAC INSTABILITY IN SUPERNOVA REMNANTS
Formation of Primordial Stars in a Lambda-CDM Universe