Electromagnetic radiation emitted (in two pulses from an air burst) from the fireball as a consequence of its very high temperature; it consists essentially of ultraviolet, visible, and infrared radiations. In the early stages (first pulse of an air burst), when the temperature of the fireball is very high, the ultraviolet predominates; in the second pulse, the temperatures are lower and most of it is in the visible and infrared regions of the spectrum.