Layer just outside the Sun's core, where energy is transported mostly in the form of radiation. This region, while too cool for fusion to occur, is still very dense and hot- about 4 million degrees Kelvin.

An interior layer of the Sun, lying between the core and the convection zone, where energy travels outward by radiation. more

the region of a star in which the energy produced by nuclear fusion in the core is carried outward by radiation. Vice versa, in the convective zone of a star the energy is carried outside by the bulk outward motions of matter.