|MadSci Network: Physics|
"Exotic radiation" is not really an official scientific designation of a specific type or class of radiation. The term is used in science fiction to denote a mysterious radiation when an actual scientific explanation is not available. Notable uses are the "McKay and Mrs. Miller" episode of the science fiction show Stargate Atlantis and in the movie "The Fantastic Four." In the realm of real science, the term "exotic radiation" would generally refer to radiation of exotic particles or normal light produced in any particularly unusual fashion. The term has been used to describe unusual occurrences of Smith-Purcell radiation, for example, produced when high-speed electrons travel through a crystal or other regular structure (the periodic variation in electric and magnetic fields within the crystal causes the electron to wiggle as it flies by, producing ordinary radio waves or microwaves). X-rays from extreme magnetic field of unusual objects like magnetar stars have occasionally been dubbed exotic radiation, though the x-rays themselves are not unusual. What's exotic is the star itself, or the spectrum of radiation produced (if it is non-thermal due to the massive magnetic field). A more accurate usage would probably be to refer to high-energy exotic particles, which typically have very short lifetimes (hence they are exotic in that they would disappear in nature). These particles are produced by high-energy cosmic rays, solar flares (though these don't typically live long enough to reach the Earth), or particle accelerators and are typically only observed because their velocities (near the speed of light) cause a relativistic time dilation. At these speeds, the particles take far longer to decay into more ordinary particles. A massive zoo of such particles can be created in high-energy particle collisions. Another more accurate usage for the term "exotic particles" could be to refer to particles whose properties have been predicted by theoretical physicists but have not yet been observed. Tachyons are a favorite to borrow from science fiction, a tachyon is a particle which always travels faster than the speed of light. Another are WIMPS (weakly interacting massive particles), which may comprise much of the dark matter which causes galaxies to rotate faster than gravitation from the ordinary matter within them can explain. WIMPS would only interact with ordinary matter very weakly, hence the reason they have never been observed.
Try the links in the MadSci Library for more information on Physics.