Atmospheric consequences of cosmic-ray variability in the extragalactic shock model / Melott Adrian L.,Krejci Alex J.,Thomas Brian C.,Medvedev Mikhail V.,Wilson Graham W.,Murray Michael J. // JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS. - 2008. - V. 113, l. E10.

ISSN/EISSN:

0148-0227 / нет данных

Type:

Article

Abstract:

It has been suggested that galactic shock asymmetry induced by our galaxy's infall toward the Virgo Cluster may be a source of periodicity in cosmic-ray exposure as the solar system oscillates normally to the galactic plane, thereby inducing an observed terrestrial periodicity in biodiversity. There are a number of plausible mechanisms by which cosmic rays might affect terrestrial biodiversity. Here we investigate one of these mechanisms, the consequent ionization and dissociation in the atmosphere, resulting in changes in atmospheric chemistry, which culminate in the depletion of ozone and a resulting increase in the dangerous solar UVB flux on the ground. We estimate the enhancement of cosmic-ray intensity for a range of reasonable parameters of the galactic wind and galactic magnetic field, and use these to compute steady-state atmospheric effects. At the lower end of this range, we find that the effects are far too small to be of serious consequence. At the upper end of this range, the level of ozone depletion approaches that currently experienced due to anthropogenic effects such as accumulated chlorofluorocarbons, i.e., similar to 2.1\% global average loss of ozone column density. We discuss some of the possible effects. While much smaller intensity than the atmospheric effects of a nearby galactic gamma-ray burst, the duration of the effects would be about 10 6 times greater. Current ozone depletion is a documented stress on the biosphere; it is not clear whether its consequences would be severe if of extended duration. We conclude that, for estimates at the upper end of the reasonable range of the cosmic-ray variability over geologic time, the mechanism of atmospheric ozone depletion may provide a small additional stress, enhancing the impact of other events. However, in order to account for large fluctuations in biodiversity correlated with cosmic-ray flux, other mechanisms should be investigated.

Author keywords:

ULTRAVIOLET-RADIATION; FOSSIL DIVERSITY; EARTHS CLIMATE; UVB RADIATION; OZONE; DECLINES; MARINE; CYCLES; CANCER; GALAXY

DOI:

10.1029/2008JE003206

Web of Science ID:

ISI:000260179700001

Соавторы в МНС:

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Другие поля

Поле	Значение
Month	OCT 15
Publisher	AMER GEOPHYSICAL UNION
Address	2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA
Language	English
Article-Number	E10007
Keywords-Plus	ULTRAVIOLET-RADIATION; FOSSIL DIVERSITY; EARTHS CLIMATE; UVB RADIATION; OZONE; DECLINES; MARINE; CYCLES; CANCER; GALAXY
Research-Areas	Geochemistry \& Geophysics
Web-of-Science-Categories	Geochemistry \& Geophysics
Author-Email	melott@ku.edu akrejci@gmail.com brian.thomas@washburn.edu medvedev@ku.edu gwwilson@ku.edu mjmurray@ku.edu
ORCID-Numbers	Thomas, Brian/0000-0001-9091-0830
Funding-Acknowledgement	Honors Program at the University of Kansas; Washburn University
Funding-Text	We thank Tanguy Pierog for assistance in our local implementation of CORSIKA. A. K. is grateful for the financial support of the Honors Program at the University of Kansas. B. T. acknowledges a Small Research Grant from Washburn University.
Number-of-Cited-References	38
Usage-Count-Since-2013	5
Journal-ISO	J. Geophys. Res.-Planets
Doc-Delivery-Number	362DZ