process has causal agent star stellar radiation microwave stellar radiation microwave solar radiation envoAstro A stellar radiation process during which electromagnetic waves or their quanta are emitted from a star at wavelengths and frequencies which travel exclusively in a line-of-sight fashion and which may produce molecular rotation and torsion on contact with matter. ENVO This definition focuses on the properties of microwaves rather than their wavelength or frequency limits. Considerable ambiguity exists around the wavelength and frequency thresholds of microwaves. The ISO 21348 definition bounds these waves at 1 mm and 15 mm, with frequencies between 100 GHz and 0.225 GHz. microwave radiation