The JPL proton fluence model: an update

The development of new technologies and the miniaturization of sensors bring new requirements for our ability to predict and forecast hazardous space weather conditions. Of particular importance are protons in the energy range from 10s to 100s of MeV which cause electronic part and solar cell degradation, and pose a hazard to biological systems in space and to personnel in polar orbit. Sporadic high-energy solar particle events are a main contributor to the fluences and fluxes of such protons. A statistical model, JPL 1991 (J. Geophys. Res. 98 (1991) 13,281), was developed to specify fluences for spacecraft design and is now widely used. Several major solar proton events have occurred since that model was developed and one objective of this paper is to see if changes need to be made in the model due to these recent events. Another objective is to review the methods used in JPL 1991 in the light of new understandings and to compare the JPL methods with those used in other models. We conclude that the method used in developing JPL 1991 model is valid and that the solar events occurring since then are completely consistent with the 1991 model. Since no changes are needed we suggest that the name of the model be changed to “the JPL fluence model”.