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Abstract
The kinetic Monte Carlo method, used in astrochemistry to investigate suprathermal (hot) particles at the molecular level, is presented. Different modifications of this method, aimed at studying the influence of suprathermal particles in the processes occurring in gas and dust envelopes surrounding astrophysical objects — prestellar and protostellar cores of molecular clouds, planets, their moons, and comets in the Solar and extrasolar planetary systems — are considered. The important role of the fraction of suprathermal particles in astrochemical applications of this approach is demonstrated. The presence of these particles leads to local changes in the chemical composition; causes non-thermal emissions in gas and dust envelopes; enhances the chemical exchange between the gas and dust fractions of envelope; leads to the formation of extended hot coronae of planets; increases non-thermal atmospheric losses, thus determining the evolution of planetary atmosphere on astronomical time scales; and facilitates the formation of complex molecules in gas and dust envelopes of astrophysical objects.
The bibliography includes 146 references.
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Kislyakova KG, Lammer H, Holmström M, Panchenko M, Odert P, Erkaev NV, Leitzinger M, Khodachenko ML, Kulikov YN, Güdel M, Hanslmeier A. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape. ASTROBIOLOGY 2013; 13:1030-48. [PMID: 24283926 PMCID: PMC3865724 DOI: 10.1089/ast.2012.0958] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates.
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Affiliation(s)
- Kristina G. Kislyakova
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
- Institute of Physics, University of Graz, Graz, Austria
| | - Helmut Lammer
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
| | | | | | - Petra Odert
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
- Institute of Physics, University of Graz, Graz, Austria
| | - Nikolai V. Erkaev
- Institute of Computational Modelling, Siberian Division of the Russian Academy of Sciences, Krasnoyarsk, Russian Federation
| | | | - Maxim L. Khodachenko
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
- SINP, Moscow State University, Moscow, Russian Federation
| | - Yuri N. Kulikov
- Polar Geophysical Institute (PGI), Russian Academy of Sciences, Murmansk, Russian Federation
| | - Manuel Güdel
- Institute of Astrophysics, University of Vienna, Austria
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