Improved Models of the Earth’s Trapped Proton Environment 1999-01-2170

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. We show in particular that the new models result in flux predictions about a factor of two higher than the old models. The new models, since they include solar cycle and secular changes, also model the geographic distribution of the proton flux more accurately.