Stellar convection: Nonuniform heating from below

An influence of a nonuniform energy flux leaving a rapidly rotating stellar core, on the subphotospheric convection zone was investigated. We used a two-dimensional, three-layer model with a convectively unstable zone sandwiched between two stable zones. Instead of a continuous energy flux distribution expected in real stars, a simplified model with a localized hot spot placed in the middle of the lower unstable zone was considered to decrease a possible influence from the side boundaries on the pattern of motion. To minimize further the effect of side boundaries a large aspect ratio 1:8 was adopted for the unstable zone. The results show that after a dynamical relaxation of the model a broad, 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 motions increase with the energy flux excess brought by the spot. Four values 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 zone may force a large scale flow of matter from the pole towards the equator in the surface layers of a rapidly rotating cool star. Horizontal distributions of radiative, convective, kinetic and total energy fluxes at different levels of the model with a hot spot are discussed.