Dynamos in resonance
Abstract
In order to investigate parametric resonance in dynamos, a simple model, where timedependent mean shear flows influence the magnetic field of an alphaOmegadynamo, is examined. The possible influence of spiral density waves on dynamo waves is studied. Dynamo models with timedependent shear flows do not lead to the classical Mathieu equation for parametric resonance. In particular, the classical resonance frequency gamma  2omega (where omega is the cycle frequency) for the shear's oscillations no longer plays a special role in the resonance effect. Only the ratio of the various components of the flow determines the stability properties. Meridional flow supports the occurrence of 'swing excitation' while the timedependent part of differential rotation acts to stabilize. The existence of parametric resonance by density waves in oscillating galactic dynamos is suggested.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 October 1992
 Bibcode:
 1992A&A...264..319S
 Keywords:

 Astronomical Models;
 Dynamo Theory;
 Interstellar Magnetic Fields;
 Orbital Resonances (Celestial Mechanics);
 Shear Flow;
 Computational Astrophysics;
 Density Distribution;
 Mathematical Models;
 Power Spectra;
 Stellar Oscillations;
 Astrophysics