A Multiscale Dynamo Model Driven by Quasi-geostrophic Convection

摘要: A convection-driven multiscale dynamo model is developed in the limit of low Rossby number for plane layer geometry which gravity and rotation vectors are aligned. The small-scale fluctuating dynamics described by a magnetically-modified quasi-geostrophic equation set, large-scale mean governed diagnostic thermal wind balance. utilizes three timescales that respectively characterize convective timescale, magnetic evolution timescale. Distinct equations derived cases order one Prandtl number. It shown characterized to kinetic energy ratio asymptotically large, with ohmic dissipation dominating viscous on large-scales. For energies equipartitioned both weak large-scales; occurs thin boundary layers adjacent solid boundaries. Elsasser small since Lorentz force does not enter leading new models can be considered fully nonlinear, generalized versions originally Childress Soward [Phys. Rev. Lett., \textbf{29}, p.837, 1972]. These may useful understanding dynamos regimes only just becoming accessible direct numerical simulations.