Sensitivity of Solar Energetic Particle Event Doses to Spectral Hardness

Doses in critical body organs of human crews in interplanetary space from energetic solar particle events (SPE) vary widely with the size and spectral hardness of the event. In this work, we present a study of the sensitivities of calculated doses to the skin, ocular lens of the eye, and bone marrow, for crewmembers in deep space, to variations in solar energetic particle event fluence levels and spectral hardness. The calculations are performed by incrementally varying the fluence levels and spectral hardness and tracking changes in organ doses as a function of these variations. For simplicity in interpreting the results, we use the rigidity parameterization form for the SPE integral fluences. It was found that for harder spectra the doses are much larger and decrease less rapidly with increased shielding.