Cherenkov light as a mechanism for light flashes seen by astronauts in space

Abstract

Astronauts first reported light flashes during the Apollo 11 mission. These events have since been associated with cosmic rays, although their underlying mechanism remains uncertain. This study investigates possible formation processes using Geant4 simulations of cosmic ray interactions in a simplified model of the human eye. We apply published models of human visual perception to the simulated particle induced photons and compare the resulting light flash rates with experimental observations. Our results indicate that, in interplanetary space and in low Earth orbit outside the South Atlantic Anomaly, Cherenkov radiation generated in the eye produces retinal responses consistent with the observed frequency of astronaut light flashes. The dominant contributing primaries are found to be high Z nuclei, primarily iron, with additional contributions from oxygen and carbon nuclei. In contrast, conditions in the South Atlantic Anomaly suggest that additional mechanisms may be required to explain observed light flashes. We also find that the absence of light flashes at Earth's surface is consistent with insufficient retinal stimulation from muon induced Cherenkov radiation under typical geometrical and flux conditions.