Density discontinuity g-modes

Density discontinuities produced by abrupt composition transitions may play an important role in determining the g-mode pulsation properties of some stars. The restoring force acting on a perturbed element of matter undergoing g-mode oscillations results from a competition between gravitational forces and buoyancy forces. Normally it is the smooth variation of entropy that is responsible for the buoyancy. If a density discontinuity is present it can locally contribute to, or even become, the dominant source of buoyancy. In the absence of 'normal' sources of buoyancy, a density discontinuity will result in a single g-mode for a given spherical harmonic index. (author)