Nonlinear dynamo theory: finite amplitude magnetic fields with large scale circulation in a compressible stratified medium.
Abstract
In the framework of the dynamo theory of the solar cycle selfconsistent numerical solutions of the nonlinear meanfield MHD equations (including Lorentz force) within a compressible stratified medium are given for a Cartesian geometry. For both steady (alphasquared) and oscillatory (alphaomega) turbulent dynamos the growth of the magnetic field is limited by a mean flow driven by the Lorentz force. Magnetic buoyancy supports this mechanism but is not able to suppress dynamo action totally or to set narrow limits to the dynamo models investigated. Flow velocities of the order of 1 m/s are sufficient to limit the magneticfield amplitude to about 10 mT (mean toroidal field of the sun). For an oscillatory dynamo of the solar type the flow pattern has a onecell geometry with fluid rising to the surface near the spot zone (zone of maximum toroidal field in the vicinity of the equator), flowing towards the pole, and sinking down there. This may account for the observed poleward motion of the prominence zone.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 1979
 Bibcode:
 1979A&A....72..348S
 Keywords:

 Dynamo Theory;
 Solar Cycles;
 Solar Magnetic Field;
 Stellar Models;
 Buoyancy;
 Compressible Flow;
 Flow Distribution;
 Magnetic Effects;
 Magnetic Flux;
 Magnetohydrodynamics;
 Solar Physics;
 Dynamo Theory:Solar Magnetic Fields;
 Solar Activity Cycles:Solar Magnetic Fields