Dynamogenerated Turbulence and LargeScale Magnetic Fields in a Keplerian Shear Flow
Abstract
The nonlinear evolution of magnetized Keplerian shear flows is simulated in a local, threedimensional model, including the effects of compressibility and stratification. Supersonic flows are initially generated by the BalbusHawley magnetic shear instability. The resulting flows regenerate a turbulent magnetic field which, in turn, reinforces the turbulence. Thus, the system acts like a dynamo that generates its own turbulence. However, unlike usual dynamos, the magnetic energy exceeds the kinetic energy of the turbulence by a factor of 310. By assuming the field to be vertical on the outer (upper and lower) surfaces we do not constrain the horizontal magnetic flux. Indeed, a largescale toroidal magnetic field is generated, mostly in the form of toroidal flux tubes with lengths comparable to the toroidal extent of the box. This largescale field is mainly of even (i.e., quadrupolar) parity with respect to the midplane and changes direction on a timescale of ∼30 orbits, in a possibly cyclic manner. The effective ShakuraSunyaev alpha viscosity parameter is between 0.001 and 0.005, and the contribution from the Maxwell stress is ∼37 times larger than the contribution from the Reynolds stress.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 1995
 DOI:
 10.1086/175831
 Bibcode:
 1995ApJ...446..741B
 Keywords:

 ACCRETION;
 ACCRETION DISKS;
 MAGNETOHYDRODYNAMICS: MHD;
 SHOCK WAVES;
 TURBULENCE