Search Results

The space radiation environment is of crucial importance to all manned and unmanned space activities. As spacecraft and their systems and instruments have become more sophisticated, they have also become more susceptible to the space radiation environment. New requirements for the radiation models have made it evident that the existing models are now inadequate. NASA, ESA, and other agencies are consequently working to develop new models. In particular, under NASA’s Space Environments and Effects (SEE) program, a new model has been developed which correctly models the solar cycle variations in the trapped proton flux at low altitudes. This model is now being merged with the U.S. Air Force model based on data from the CRRES satellite; the resulting model will be a replacement for the current models. In this paper we present a review of the new and existing models and compare them with each other and with available data.

Solar flares which produce significant numbers of energetic protons are accompanied by optical, radio and x-ray emissions. Thus the capability for providing early warning of solar proton events (SPEs) is possible if the particle fluxes can be correlated with the electromagnetic signatures from the sun. We have continued to develop and refine the correlations between the proton fluxes in the SPE's and their electromagnetic emissions. Data from over most of solar cycle 21 and the early portion of cycle 22 have been used to extend our data base and improve the correlations between peak proton fluxes and the x-ray fluences which arrive at the earth earlier than the protons. A simple relationship has been derived between the probability of occurrence of an SPE and the observed x-ray fluence.