If Type is set to Radiation, then the dialog will look as shown below.
Radiation loads can be applied to surfaces and curves. Radiation loads can only be applied in heat transfer analyses. Radiation to the open environment is supported, but not surface-to-surface radiation. Radiation is a nonlinear effect and requires the use of nonlinear steady state or transient heat transfer. If used in linear steady state heat transfer, the results will be incorrect.
The ambient temperature can be time dependent when nonlinear transient heat transfer is selected as the analysis type. Only Emissivity can be temperature dependent in nonlinear heat transfer analysis.
Radiation loads can have custom display properties such as color, size, and density.