STELLAR CONVECTION - NONUNIFORM HEATING FROM BELOW

An influence of a nonuniform energy flux leaving a rapidly rotating st ellar core, on the subphotospheric convection zone was investigated. W e used a two-dimensional, three-layer model with a convectively unstab le zone sandwiched between two stable zones. Instead of a continuous e nergy flux distribution expected in real stars, a simplified model wit h a localized hot spot placed in the middle of the lower unstable zone was considered to decrease a possible influence from the side boundar ies on the pattern of motion. To minimize further the effect of side b oundaries a large aspect ratio 1:8 was adopted for the unstable zone. The results show that after a dynamical relaxation of the model a broa d, stable updraft above the hot spot is formed. It induces large scale circulations involving horizontal motions from the spot axis near the top of the convection zone. The extend and kinetic energy of these mo tions increase with the energy flux excess brought by the spot. Four v alues of the flux excess were considered: 0.1, 0.3, 1.0 and 3.0. It is suggested that the nonuniform energy flux entering the convection zon e may force a large scale flow of matter from the pole towards the equ ator in the surface layers of a rapidly rotating cool star. Horizontal distributions of radiative, convective, kinetic and total energy flux es at different levels of the model with a hot spot are discussed.