Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-08-18
Smith, D.S., and Scalo, J.M. (2004) Icarus, 171, 229
Astronomy and Astrophysics
Astrophysics
59 pages, 15 figures; in press in Icarus; minor edits, no results changed
Scientific paper
10.1016/j.icarus.2004.04.009
(Abridged) The propagation of ionizing radiation through model atmospheres of terrestrial-like exoplanets is studied for a large range of column densities and incident photon energies using a Monte Carlo code we have developed to treat Compton scattering and photoabsorption. Incident spectra from parent star flares, supernovae, and gamma-ray bursts are modeled and compared to energetic particles in importance. We find that terrestrial-like exoplanets with atmospheres thinner than about 100 g cm^-2 transmit and reprocess a significant fraction of incident gamma-rays, producing a characteristic, flat surficial spectrum. Thick atmospheres (>~ 100 g cm^-2) efficiently block even gamma-rays, but nearly all incident energy is redistributed into diffuse UV and visible aurora-like emission, increasing the effective atmospheric transmission by many orders of magnitude. Depending on the presence of molecular UV absorbers and atmospheric thickness, up to 10% of the incident energy can reach the surface as UV reemission. For the Earth, between 2 x 10^-3 and 4 x 10^-2 of the incident flux reaches the ground in the biologically effective 200--320 nm range, depending on O_2/O_3 shielding. Finally, we suggest that transient atmospheric ionization layers can be frequently created at low altitudes. We conclude that these events can produce frequent fluctuations in atmospheric ionization levels and surficial UV fluxes on terrestrial-like planets.
Scalo John
Smith David S.
Wheeler Justin C.
No associations
LandOfFree
Transport of Ionizing Radiation in Terrestrial-like Exoplanet Atmospheres does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Transport of Ionizing Radiation in Terrestrial-like Exoplanet Atmospheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transport of Ionizing Radiation in Terrestrial-like Exoplanet Atmospheres will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-384694