A Sufficient Condition for Instability in a Sheared Incompressible Magnetofluid
Abstract
It is shown that a sufficient condition for the stability of an incompressible sheared gravitationally stratified ideal magnetofluid with flow-aligned horizontal magnetic field is that there exists a Galilean frame in which the flow is nowhere super-Alfvénic (similarly, stability is assured in a compressible shear flow without gravity if there exists a frame in which the flow nowhere exceeds the cusp speed). Complex eigenvalue bounds are presented for unstable flows. The stability condition is applied to the solar tachocline; it suggests that any shear instabilities associated with radial gradients in flow speed should be stabilized by fields of above about 7 kG.
- Publication:
-
Solar Physics
- Pub Date:
- June 2000
- DOI:
- 10.1023/A:1005291530412
- Bibcode:
- 2000SoPh..194..189C
- Keywords:
-
- Magnetic Field;
- Assure;
- Stability Condition;
- Shear Flow;
- Flow Speed