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| Paper: |
Interchange Method in Compressible Magnetized Couette Flow: Magnetorotational and Magnetoconvective Instabilities |
| Volume: |
290, Active Galactic Nuclei: from Central Engine to Host Galaxy |
| Page: |
105 |
| Authors: |
Kazanas, D.; Christodoulou, D.; Contopoulos, J. |
| Abstract: |
We obtain the general form of the axisymmetric stability criteria in a magnetized, compressible Couette flow using a variational principle, the so-called interchange method, which we applied successfully in the incompressible case in the past. This formulation accounts for the simultaneous presence of gravity, rotation, entropy and density gradients, a toroidal magnetic field and a weak axial magnetic field in its initial equilibrium state. The crucial aspect of the method is its explicit implementation of the relevant conservation laws in the computation of the "free energy" of the system in its original equilibrium. As in the incompressilbe case, the presence of an axial field invalidates the conservation laws of angular momentum and azimuthal magnetic flux, introducing instead isorotation and axial current conservation along field lines. The stability criteria are therefore markedly different depending on whether an axial magnetic field is present. In limiting cases our formulation transparently recovers the convective and Parker instability criteria, as well as those of Newcomb and Terkovnikov pertaining to rotating magnetized plasmas derived through the implementation of much more laborious techniques. |
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