Electrodynamics of turbulent fluids with fluctuating electric conductivity
Abstract
Consequences of fluctuating microscopic conductivity in meanfield electrodynamics of turbulent fluids are formulated and discussed. If the conductivity fluctuations are assumed to be uncorrelated with the velocity fluctuations then only the turbulenceoriginated magnetic diffusivity of the fluid is reduced and the decay time of a largescale magnetic field or the cycle times of oscillating turbulent dynamo models are increased. If, however, the fluctuations of conductivity and flow in a certain welldefined direction are correlated, an additional diamagnetic pumping effect results, transporting the magnetic field in the opposite direction to the diffusivity flux vector $\langle \unicode[STIX]{x1D702}^' }\boldsymbol{u}^' }\rangle$. In the presence of global rotation, even for homogeneous turbulence fields, an alpha effect appears. If the characteristic values of the outer core of the Earth or the solar convection zone are applied, the dynamo number of the new alpha effect does not reach supercritical values to operate as an $\unicode[STIX]{x1D6FC}^{2}$dynamo but oscillating $\unicode[STIX]{x1D6FC}\unicode[STIX]{x1D6FA}$dynamos with differential rotation are not excluded.
 Publication:

Journal of Plasma Physics
 Pub Date:
 June 2020
 DOI:
 10.1017/S0022377820000665
 arXiv:
 arXiv:1911.06611
 Bibcode:
 2020JPlPh..86c9018R
 Keywords:

 astrophysical plasmas;
 plasma flows;
 Physics  Plasma Physics;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Fluid Dynamics
 EPrint:
 11 pages, 4 figures