Magnetic Field Transfer by TwoDimensional Convection and Solar 'SemiDynamo'
Abstract
A comparison of the equations for the magnetic field transfer and for the heat transfer by twodimensional turbulent convection of a conducting compressible medium shows the magnetic field to be transported as a scalar admixture provided it is parallel to the convective rolls. At high magnetic Reynolds numbers the field strength in a convective zone varies proportionally to the density of the medium. A study of the distribution and amplification of the poloidal field in the twodimensional convection zone of the Sun lying under the supergranulation, together with the processes of field pumping and amplification in other zones, reveals the importance of considering generation mechanisms of thesemidynamo type where the amplifying field is excited independently by weak e.m.f.'s of nonelectric origin with no feedback which would otherwise produce MHD selfexcitation of the field. An illustrative calculation of the solar poloidal field maintained by a weak Coriolis e.m.f. acting in a thin external layer of the convective envelope yields for the general nearpolar field, if one somehow takes into account (1) field pumping by threedimensional supergranulation, (2) field transfer and amplification by twodimensional convection, and (3) ohmic diffusion of the field into a stable core, a value of the order of 10^{1} gauss.
 Publication:

Astrophysics and Space Science
 Pub Date:
 January 1977
 DOI:
 10.1007/BF00643752
 Bibcode:
 1977Ap&SS..46...41D
 Keywords:

 Convective Flow;
 Dynamo Theory;
 Heat Transfer;
 Solar Atmosphere;
 Solar Granulation;
 Solar Magnetic Field;
 Coriolis Effect;
 Magnetohydrodynamic Flow;
 Self Excitation;
 Solar Physics;
 Turbulent Diffusion;
 Turbulent Flow;
 Astrophysics