Strange Modes in Pulsating Stars

Abstract:

The problem of a pulsating star is very similar to that of a wind instrument,
such as a trumpet, and both can be described by a Webster-Bernoulli (or
Schroedinger) equation.  In the case of the pulsating star the 'potential' has
a sharp variation close to the surface which lets some modes (strange modes) be
trapped in the surface region.

Linear calculations show that these strange, or surface modes can be
self-excited.  Nonlinear hydrodynamical simulations show that they grow to
small, but observable pulsation amplitudes, even when turbulent convection is
included and when realistic leaky surface boundary conditions are imposed.