Single event upsets caused by solar energetic heavy ions

We calculate single event upset (SEU) rates due to protons, alphas, and heavier ions in two satellite systems for the major solar particle events of 1989-92, using a new and complete analysis of GOES proton data and high-energy heavy-ion fluences from the University of Chicago Cosmic Ray Telescope on IMP-8. These measurements cover the entire range of energies relevant to SEU studies and therefore overcome shortcomings of previous studies, which relied upon theoretical or semi-empirical estimates of high-energy heavy-ion spectra. We compare our results to the observed SEU rates in these events. The SEU rates in one device (AMD 93L422s on LEASATs) were overwhelmingly dominated by protons. However, even after taking into account uncertainties in the ground-test cross-section data, we find that at least ~45% of the SEUs in the other device (Fairchild 93L422s on TDRS-1) must have been caused by heavy ions. Our results demonstrate that both protons and heavy ions must be considered in order to make a reliable assessment of SEU vulnerabilities. Furthermore, the GOES/Chicago database of solar particle events provides a basis for making accurate solar particle SEU calculations and credible worst-case estimates. In particular, measurements of the historic solar particle events of October 1989 are used in “worst week” and “worst day” environment models in CREME96, a revision of NRL´s Cosmic Ray Effects on MicroElectronics code