Nondiffusive angular momentum transport in rotating pinches
Abstract
The stability of conducting TaylorCouette flows under the presence of toroidal magnetic background fields is considered. For strong enough magnetic amplitudes such magnetohydrodynamic flows are unstable against nonaxisymmetric perturbations which may also transport angular momentum. In accordance with the often used diffusion approximation, one expects the angular momentum transport to be vanishing for rigid rotation. In the sense of a nondiffusive effect, however, even for rigidly rotating pinches, an axisymmetric angular momentum flux appears which is directed outward (inward) for large (small) magnetic Mach numbers. The internal rotation in a magnetized rotating tank can thus never be uniform. Those particular rotation laws are used to estimate the value of the instabilityinduced eddy viscosity for which the nondiffusive effect and the diffusive shearinduced transport compensate each other. The results provide the Shakura & Sunyaev viscosity ansatz leading to numerical values linearly growing with the applied magnetic field.
 Publication:

Journal of Plasma Physics
 Pub Date:
 December 2019
 DOI:
 10.1017/S0022377819000606
 arXiv:
 arXiv:1907.08291
 Bibcode:
 2019JPlPh..85f9001R
 Keywords:

 plasma instabilities;
 astrophysical plasmas;
 Physics  Plasma Physics;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Fluid Dynamics
 EPrint:
 15 pages, 9 figures