Study of the equilibrium and motions of the medium in a rotating star witha magnetic field using tools from angular momentum theory

The complicated processes occurring in a rotating magnetized medium are exa mined by representing all the vector quantities in the form of expansions i n a complete system of orthogonal vector spherical harmonics. A separation of variables is ultimately achieved without a loss of accuracy despite the presence of nonlinear forces (the magnetic and Coriolis forces). The distri bution of the rates of rotation and circulation motions in an adiabatically stratified, slowly rotating star or an atmospheric convection zone is stud ied as an example. The postulate of minimum entropy production from nonequi librium thermodynamics is employed to find the most probable steady-state c onfiguration. One solution satisfactorily describes the differential rotati on observed on the Sun. The preliminary data support the notion that the su perfast rotation of the type observed in Venus' atmosphere can also be expl ained within the theory discussed. (C) 1999 American Institute of Physics. [S1063-7842(99)00409-2].