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17 April 2024 |
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Article overview
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Galactic cosmic rays on extrasolar Earth-like planets: II. Atmospheric implications | | J.--M. Grießmeier
; F. Tabataba-Vakili
; A. Stadelmann
; J. L. Grenfell
; D. Atri
; | | Date: |
21 Mar 2016 | | Abstract: | (abridged abstract) Theoretical arguments indicate that close-in terrestial
exoplanets may have weak magnetic fields. As described in the companion article
(Paper I), a weak magnetic field results in a high flux of galactic cosmic rays
to the top of the planetary atmosphere. We investigate effects that may result
from a high flux of galactic cosmic rays both throughout the atmosphere and at
the planetary surface. Using an air shower approach, we calculate how the
atmospheric chemistry and temperature change under the influence of galactic
cosmic rays for Earth-like (N_2-O_2 dominated) atmospheres. We evaluate the
production and destruction rate of atmospheric biosignature molecules. We
derive planetary emission and transmission spectra to study the influence of
galactic cosmic rays on biosignature detectability. We then calculate the
resulting surface UV flux, the surface particle flux, and the associated
equivalent biological dose rates. We find that up to 20% of stratospheric ozone
is destroyed by cosmic-ray protons. The reduction of the planetary ozone layer
leads to an increase in the weighted surface UV flux by two orders of magnitude
under stellar UV flare conditions. The resulting biological effective dose rate
is, however, too low to strongly affect surface life. We also examine the
surface particle flux: For a planet with a terrestrial atmosphere, a reduction
of the magnetic shielding efficiency can increase the biological radiation dose
rate by a factor of two. For a planet with a weaker atmosphere (with a surface
pressure of 97.8 hPa), the planetary magnetic field has a much stronger
influence on the biological radiation dose, changing it by up to two orders of
magnitude. | | Source: | arXiv, 1603.6500 | | Services: | Forum | Review | PDF | Favorites | |
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