Let Analyses of Biological Damage During Solar Particle Events

Solar particle events (SPE) are typically dominated by high-energy, low-linear energy transfer (LET) protons. Biological damage to astronauts during an SPE is expected to include a large contribution from high LET target fragments produced in nuclear reactions in tissue. We study the effects of nuclear reactions on integral LET spectra, behind typical levels of spacecraft and body shielding, for the historically largest flares using the high-energy transport code, BRYNTRN in conjunction with several biological damage models. The cellular track model of Katz provides an accurate description of cellular damage from heavy ion exposure. The track model is applied with BRYNTRN to provide an LET decomposition of survival and transformation rates for solar proton events. In addition, a fluence-based risk coefficient formalism is used to estimate Harderian gland tumor induction in rodents and cataractogenesis in rabbits from solar flares, and a LET analysis is used to assess the relative contribution from target fragments on these biological endpoints.