A sharp pulse of radio-frequency (long wavelength) radiation produced when an explosion occurs in an asymmetrical environment, especially at or near the earth's surface or at high altitudes. The intense electric and magnetic fields can damage unprotected electrical and electronic equipment over a large area. It is now thought that a single high-altitude blast over the U. S. could seriously disrupt the nation's communications system, and perhaps shut down the entire power grid. At present, however, there is no known way of providing complete protection against the effect.

See Electron.