Convection is the transport of heat by turbulent motion of gas. Within stars, this thermal energy is supplied either by nuclear fusion or bulk gravitational contraction. The luminosity of the Sun is carried outward by convection in the outer third of its radius. The shifting pattern of granulation visible on the solar surface represents rising and falling gas cells in the convection zone. The upwelling of gas in this zone, together with the Sun’s rotation, amplifies and maintains the solar magnetic field. When the Sun was a pre-main-sequence star, its relatively high surface cooling drove convection throughout its interior.
Stars generate energy by nuclear fusion or gravitational contraction. This energy is transported through the interior, eventually streaming outward as radiation from the surface. The transport occurs either through the diffusion of radiation or convection. In the Sun, whose luminosity stems entirely from fusion, convection operates in the outer...