ment. Fortunately, the flux of these HZE particles is low and is unlikely to be affected by artificial magnetospheric modification. Relativistic electrons, on the other hand, constitute a component as important as HZE particles in defining design limits to space systems. As was pointed out previously relativistic electrons are rather more likely to interact with magnetospheric turbulence by resonant pitch-angle scattering with ion cyclotron waves; therefore, ring current and thermal plasma modifications are likely to impact Van Allen belt relativistic electrons. The present population of such hazardous electrons is kept in balance by the occurrence of several large magnetic storms per year. During such large storms, relativistic electrons in the. radiation belts are seen to precipitate into the atmosphere. Such an event is known as an REP (relativistic electron precipitation) event. Suppression of the proton-cyclotron instability might, therefore, result in a major enhancement of the radiation level from relativistic electrons within a year after argon-ion saturation of the plasmasphere. The enhancement of relativistic-electron radiation can be analyzed within the framework of a simple model. Consider the model equation (e.g., Schulz, 1974) [[spi:math]] (51) in which I represents the radiation intensity, [[spi:math]] the natural radiation-belt decay rate, and S the strength of a weak source of relativistic electrons. The decay rate [[spi:math]] is perhaps inversely proportional to the particle energy E, such that [[spi:math]] x 10 days. The solution of (51) approaches the limit [[spi:math]]. Suppose, however, that I is reduced to zero by relativistic electron precipitation (REP) events, which occur randomly in 53
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