Solar flare proton evaluation at geostationary orbits for engineering applications

Abstract

Presents the results of novel analyses of spacecraft solar flare proton measurements for solar cycles 20, 21, and 22. Solar events and cycles were classified and ranked by fluence and frequency of occurrence, and events were characterized by the mean energy of the proton spectral distributions. Spacecraft observations permitted a detailed study of event characteristics, such as special consideration of solar minimum flares and cycle variability. Tables and curves are presented to allow evaluations of potential threats to spacecraft survivability at GEO, particularly for types of flare environments that emulate solar cycle 22. Upsets for major events are calculated for several Bendel A parameter values and shield thicknesses, and effective energy thresholds of events are determined as a function of these variables. Critical fluence levels, required to cause errors, versus A are presented. Single event upsets of 93L422 devices on TDRS-1 are evaluated for various shielding conditions. Finally, upset dependencies on A and shield thickness are correlated with event fluences for threshold energies of >30, >50, and >60 MeV.