Hypothetical worst case solar particle event doses in LE0

Abstract

For over two decades, hypothetical models of "worst case" solar particle event (SPE) spectra have been proposed in order to place an upper bound on radiation doses to crews on space missions. These event spectra are usually formulated using hypothetical extrapolations of space measurements for previous large events, which have occurred during or just prior to the space era. In this work we take a different approach. Recently reported analyses of ice core samples indicate that the Carrington flare of 1859 is the largest event observed in the past 500 years. These ice core data yield estimates of the proton fluence for energies greater than 30 MeV, but provide no other spectrum information. Assuming that the proton energy distribution for such an event is similar to that measured for other recent, large events, critical body organ doses for crews in representative LEO missions are estimated for these hypothetical worst-case SPE spectra. If the event is accompanied by a substantial geomagnetic storm, these estimated doses are large and could be mission threatening unless substantial shielding is provided.