SOLAR PROTON EVENTS AND THEIR EFFECT ON SPACE SYSTEMS

Solar protons present a major problem to space systems because of the ionisation and displacement effects which arise from their interaction with matter. This is likely to become a greater problem in the future due to the use of more sensitive electronic components and the propos ed expansion of manned activities in space. An outline is provided of the physical processes associated with individual solar events, the so lar activity cycle and the transport of solar particles between the Su n and the Earth. The problems of predicting solar event fluences, both over short- and long-term periods, are discussed. The currently avail able solar proton event models used for long-term forecasting are brie fly reviewed, and the advantages and deficiencies of each model are in vestigated. Predictions using the models are compared to measurements made by the GOES-7 satellite during the rising phase of the current so lar cycle. These measurements are also used to illustrate the sensitiv ity of the models to the choice of confidence level and to the spectra l form used for extrapolation over the solar proton energy range.