Solar irradiance changes and photobiological effects at Earth's surface following astrophysical ionizing radiation events

Abstract

Astrophysical ionizing radiation events have been recognized as a potential threat to life on Earth, primarily through depletion of stratospheric ozone and subsequent increase in surface-level solar ultraviolet radiation. Simulations of the atmospheric effects of a variety of events (such as supernovae, gamma-ray bursts, and solar proton events) have been previously published, along with estimates of biological damage at Earth's surface. In this work, we employed the TUV radiative transfer model to expand and improve calculations of surface-level irradiance and biological impacts following an ionizing radiation event. We considered changes in surface-level UVB, UVA, and photosynthetically active radiation (visible light) for clear-sky conditions and fixed aerosol parameter values. We also considered a wide range of biological effects on organisms ranging from humans to phytoplankton. We found that past work overestimated UVB irradiance, but that relative estimates for increase in exposure to DNA damaging radiation are still similar to our improved calculations. We also found that the intensity of biologically damaging radiation varies widely with organism and specific impact considered; these results have implications for biosphere-level damage following astrophysical ionizing radiation events. When considering changes in surface-level visible light irradiance, we found that, contrary to previous assumptions, a decrease in irradiance is only present for a short time in very limited geographical areas; instead we found a net increase for most of the modeled time-space region. This result has implications for proposed climate changes associated with ionizing radiation events.

In press at Astrobiology

References in corpus (5)

• Astrophysical Ionizing Radiation and the Earth: A Brief Review and Census of Intermittent Intense Sources
• Modeling atmospheric effects of the September 1859 Solar Flare
• Climatic and Biogeochemical Effects of a Galactic Gamma-Ray Burst
• Superluminous supernovae: No threat from Eta Carinae
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Cited by in corpus (6)

• Risks for life on habitable planets from superflares of their host stars
• Terrestrial Effects Of Nearby Supernovae In The Early Pleistocene
• Astrobiological Effects of Gamma-Ray Bursts in the Milky Way Galaxy
• Reductions in Depth-integrated Picophytoplanktonic Photosynthesis Due to Inhibition by Ultraviolet and Photosynthetically Available Radiation: Global Predictions for $\text{Prochlorococcus}$ and $\text{Synechococcus}$
• Photobiological effects at Earth's surface following a 50 pc Supernova
• Atmospheric constituents and surface-level UVB: implications for a paleoaltimetry proxy and attempts to reconstruct UV exposure during volcanic episodes