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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L14808, doi:10.1029/2005GL023073, 2005

Climatic and biogeochemical effects of a galactic gamma ray burst

Adrian L. Melott

Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA


Brian C. Thomas

Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA


Daniel P. Hogan

Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA


Larissa M. Ejzak

Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA


Charles H. Jackman

Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


Abstract

It is likely that one or more gamma ray bursts within our galaxy have strongly irradiated the Earth in the last Gy. This produces significant atmospheric ionization and dissociation, resulting in ozone depletion and DNA-damaging ultraviolet solar flux reaching the surface for up to a decade. Here we show the first detailed computation of two other significant effects. Visible opacity of NO2 is sufficient to reduce solar energy at the surface up to a few percent, with the greatest effect at the poles, which may be sufficient to initiate glaciation. Rainout of dilute nitric acid could have been important for a burst nearer than our conservative “nearest burst”. These results support the hypothesis that the characteristics of the Late Ordovician mass extinction are consistent with GRB initiation.

Received 24 March 2005; accepted 24 June 2005; published 21 July 2005.

Index Terms: 7554 Solar Physics, Astrophysics, and Astronomy: X-rays, gamma rays, and neutrinos; 0764 Cryosphere: Energy balance; 0469 Biogeosciences: Nitrogen cycling; 3344 Atmospheric Processes: Paleoclimatology (0473, 4900); 9620 Information Related to Geologic Time: Ordovician.

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Citation: Melott, A. L., B. C. Thomas, D. P. Hogan, L. M. Ejzak, and C. H. Jackman (2005), Climatic and biogeochemical effects of a galactic gamma ray burst, Geophys. Res. Lett., 32, L14808, doi:10.1029/2005GL023073.