Geophysical and Astrophysical Applications and Analogies
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All natural object are rotating. The range of the periods of them allowing hydrodynamic description spreads from milliseconds (neutron stars) to many months (e.g. the planet Venus with a period of 224 days = 1.94 · 107sec) differing by ten orders of magnitude, or even more. If the source of motions is internal, the convection, at least in small scales (compared to the size of the object), can be considered as free. If the main source of energy is external, as the Sun for the planetary atmospheres, the free convection can be observed only in boundary layers above the planetary surface, or above the layer where the absorption of the solar radiation per unit mass is maximal as for deep atmospheres. The global inhomogeneity of heating of a spherical planetary atmosphere by an external source like the Sun causes a global circulation of the atmosphere. Regimes and patterns of the atmospheric circulation can be classified depending on the object and its atmospheric properties and the source intensity (Golitsyn,1970,1973). Cases are possible when internal and external heat sources are comparable in their intensities (e.g. Jupiter, Saturn, Neptune). Then, a prevailing of the small scale convection or the atmospheric general circulation in their kinetic energies per unit mass depends on the height and the atmospheric composition determining the absorption of the external (solar) and internal thermal radiation.
KeywordsNusselt Number Neutron Star Rayleigh Number Accretion Disk Deep Convection
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