Mean-field electrodynamics of fluids with fluctuating electric conductivity. (arXiv:1911.06611v1 [physics.plasm-ph])
<a href="http://arxiv.org/find/physics/1/au:+Rudiger_G/0/1/0/all/0/1">G. Rüdiger</a>, <a href="http://arxiv.org/find/physics/1/au:+Kuker_M/0/1/0/all/0/1">M. Küker</a>, <a href="http://arxiv.org/find/physics/1/au:+Kapyla_P/0/1/0/all/0/1">P. J. Käpylä</a>
The influence of fluctuating conductivity on the coefficients known from the
mean-field electrodynamics is considered. If the conductivity fluctuations are
assumed as uncorrelated with the turbulent velocity field then only the
effective magnetic diffusivity of the fluid is reduced and the decay time of a
large-scale magnetic field is increased. If the fluctuations of conductivity
and flow are correlated in a certain direction then an additional diamagnetic
pumping effect results transporting magnetic field in opposite direction to the
resistivity flux vector $langle eta’vec{u}’rangle$. Even for homogeneous
turbulence fields in the presence of rotation an $alpha$ effect appears. With
the characteristic values of the outer Earth core or the solar convection zone,
however, the dynamo number of the new $alpha$ effect never reaches
supercritical values to operate as an $alpha^2$-dynamo.
The influence of fluctuating conductivity on the coefficients known from the
mean-field electrodynamics is considered. If the conductivity fluctuations are
assumed as uncorrelated with the turbulent velocity field then only the
effective magnetic diffusivity of the fluid is reduced and the decay time of a
large-scale magnetic field is increased. If the fluctuations of conductivity
and flow are correlated in a certain direction then an additional diamagnetic
pumping effect results transporting magnetic field in opposite direction to the
resistivity flux vector $langle eta’vec{u}’rangle$. Even for homogeneous
turbulence fields in the presence of rotation an $alpha$ effect appears. With
the characteristic values of the outer Earth core or the solar convection zone,
however, the dynamo number of the new $alpha$ effect never reaches
supercritical values to operate as an $alpha^2$-dynamo.
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