Turbulent Dynamos and Magnetic Helicity
Author: Hantao Ji
It is shown that the turbulent dynamo alpha-effect converts magnetic helicity from the turbulent field to the mean field when the turbulence is electromagnetic while the magnetic helicity of the mean-field is transported across space when the turbulence is electrostatic or due to the electron diamagnetic effect. In all cases, however, the dynamo effect strictly conserves the total helicity except for a battery effect which vanishes in the limit of magnetohydrodynamics. Implications for astrophysical situations, especially for the solar dynamo, are discussed.