The Electromagnetic Pulse and Its Effects

INTRODUcnON ing was halted in 1962. Subsequently, 11.01 Explosions of conventional reliance has been placed on underhigh explosives can produce electroground testing, analysis of existing atmagnetic signals and so the generation mospheric test data, nonnuclear simulaof an electromagnetic pulse (EMP) from tion, and theoretical calculations. a nuclear detonation was expected. Extended efforts have been made to imHowever, the extent and potentially prove theoretical models and to develop serious nature of EMP effects were not associated computer codes for predicrealized for several years. Attention tive studies. In addition, simulators slowly began to focus on EMP as a have been developed which are capable probable cause of malfunction of elecof producing representative pulses for tronic equipment during atmospheric system coupling and response studies. nuclear tests in the early 1950's. In11.03 Nuclear explosions of all duced currents and voltages caused untypes -from underground to high altiexpected equipment failures and subsetudes -are accompanied by an EMP, quent analysis disclosed the role of EMP although the intensity and duration of in such failures. Finally, around 1960 the pulse and the area over which it is the possible vulnerability of various cieffective vary considerably with the 10vilian and military electrical and eleccation of the burst point. The strongest tronic systems to EMP was recognized. electric fields are produced near the At about the same time it became apburst by explosions at or near the earth's parent that the EMP could be used in the surface, but for those at high altitudes long-range detection of nuclear detonathe fields at the earth' s surface are strong tions. enough to be of concern for electrical 11.02 For the foregoing reasons, and electronic equipment over a very theoretical and experimental efforts much larger area. have been made to study the EMP and 11.04 The nuclear EMP is a timeits effects. A limited amount of data had varying electromagnetic radiation which been gathered when aboveground testincreases very rapidly to a peak and then