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J. Leliwa-Kopystynski (Institute of Geophysics, University of Warsaw, Poland, and Space Research Center of PAS, Warsaw, Poland), L. Czechowski (Institute of Geophysics, University of Warsaw, Poland)
We consider the satellites of the size range from Mimas or Protheus (radii 200 km) to Titania (790 km). The lower limit is that of the smallest sphere-like bodies. The upper limit is determined by requirement that no phase transitions occurs inside the body or these transitions are only of marginal significance. Therefore, the considered bodies could be 6 satellites of Saturn, 5 of Uranus, Protheus, and Charon. Since Miranda is probably a re-accretion product and density of Protheus is unknown therefore our class of satellites contains 11 globes in total. Their densities are known and therefore the mass ratio rock/total and radioactive heat production can be estimated quite well. Two extreme models of the satellites are considered: non-differentiated (homogeneous) and fully differentiated with rocky core and icy mantle. For the first model there is a uniform distributions of radioactive sources and the convection can develop within the whole globe. For the second case, the radioactivity determines the heat flux through the boundary between rocky core and icy mantle; in this case the possibilities of convection are discussed within the icy mantle. Axially symmetric convection is considered. The model is based on the equations: Navier-Stokes, thermal conductivity, mass continuity, and on the equation of state. They involved a large set of parameters of which the viscosity is the least known and it is strongly dependent on temperature. Written in dimensionless form for constant viscosity the equations have only one parameter, the Rayleigh number Ra. Set of solutions, for different Ra, and for constant viscosity or for temperature dependent viscosity are presented. The solutions, when converted into dimensional form, are applied for interpretation of particular tectonic features on the icy satellites (e.g. Samarkand Sulci on Enceladus and Ithaca Chasma on Tethys). Correlation between tectonic features and far-near sides orientation is expected.