Nonlinear diffusive instabilities in differentially rotating stars |
| |
| Authors: | E Knobloch |
| |
| Institution: | Max-Planck-Institut für Physik u. Astrophysik, Institut für Astrophysik , 8046, Garching, West Germany |
| |
| Abstract: | Abstract Angular momentum driven instabilities in a stratified differentially rotating star are investigated. In the strong buoyancy limit axisymmetric instabilities of the Goldreich-Schubert type are the most important. A detailed discussion of the linear and small amplitude theories at an arbitrary latitude is given. The bifurcation to finite amplitude steady modes is typically transcritical, and occurs whenever the angular momentum or its gradient is neither parallel not perpendicular to local gravity. Such misalignments enhance the time scale for transport of angular momentum by the Goldreich-Schubert instability. Depending on the turbulent viscosity produced by secondary shear instabilities time scales as short as the Kelvin-Helmholtz time scale are possible. |
| |
| Keywords: | Lie derivative potential vorticity helicity potential magnetic field |
|
|
