We have studied the influence of the dissipation number on the behaviour of a~magnetohydrodynamic system in a rotating liquid Cartesian box in the presence of afinitely conducting solid box beneath the liquid. The dissipation number appears in dimensionless description of the three physical mechanisms in the heat equation: the adiabatic heating/cooling, the dissipative heating and the Joule heating. We have demonstrated that the adiabatic heating/cooling can strongly suppress the horizontal gradient of temperature, if the surface temperature is of the same order as the temperature drop over the liquid layer. This effect stabilizes the convection pattern. the influence of dissipation is negligible. We hypothesize that the adiabatic heating/cooling could be the substantial stabilizing mechanism in systems with a~high Rayleigh number, which seem to be suitable for the description of the magnetohydrodynamics of the Earth's core.
Keyword(s): Dynamo theory; Magnetoconvection; Dissipation number
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