Cycle times and magnetic amplitudes in nonlinear 1D α^2^{OMEGA}dynamos.
Abstract
A nonlinear, 1Dslab, α^2^{OMEGA}dynamo is analysed for magnetic field amplitudes and for the relation between the cycle time and the dynamo number. If the only nonlinearity is the conventional αquenching, the magnetic field strongly grows with the dynamo number, while the dependence of the cycle time is only rather weak. The opposite is true if the nonlinear feedback is more consistently included: the complete effect of the turbulent EMF tensor is deformed and suppressed by the induced largescale magnetic field. In particular, this involves ηquenching where the eddy diffusivity becomes a tensor whose component are different functions of the magnetic field. Thus, the magnetic field amplitude only scales with the small value m'=<0.2 while the cycle oscillation frequency depends much more strongly on the dynamo number (n'~0.5). The latter seems to be consistent with the results of the Mt. Wilson HKproject for stellar activity cycles, although our dynamo model only forms a rather rough approximation for stellar configurations.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 December 1996
 Bibcode:
 1996A&A...316L..17R
 Keywords:

 TURBULENCE;
 STARS: ACTIVITY;
 STARS: MAGNETIC FIELDS;
 GALAXIES: MAGNETIC FIELDS