Труды сотрудников ИВМ СО РАН

[Text] / H. . Lammer [et al.] // Astrobiology. - 2007. - Vol. 7, Is. 1. - P185-207, DOI 10.1089/ast.2006.0128. - Cited References: 104 . - ISSN 1531-1074РУБ Astronomy & Astrophysics + Biology + Geosciences, Multidisciplinary

Аннотация: Atmospheric erosion Of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wavelengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 mu m band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O+ ion pick up at orbital distances <= 0.2 astronomical units. We have found that, when exposed to intense XUV fluxes, atmospheres with CO2/N-2 mixing ratios lower than 96% will show an increase in exospheric temperatures and expanded thermosphere-exosphere environments. Hence, they suffer stronger atmospheric erosion, which can result in the total loss of several hundred bars even if an exoplanet is protected by a "magnetic shield" with its boundary located at I Earth radius above the surface. Furthermore, our study indicates that magnetic moments of tidally locked Earth-like exoplanets are essential for protecting their expanded upper atmospheres because of intense XUV radiation against CME plasma erosion. Therefore, we suggest that larger and more massive terrestrial-type exoplanets may better protect their atmospheres against CMEs, because the larger cores of such exoplanets would generate stronger magnetic moments and their higher gravitational acceleration would constrain the expansion of their thermosphere-exosphere regions and reduce atmospheric escape.


Доп.точки доступа:
Lammer, H.; Lichtenegger, H.I.M.; Kulikov, Y.N.; Griessmeier, J.M.; Terada, N.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Khodachenko, M.L.; Ribas, I.; Penz, T.; Selsis, F.

/ I. F. Shaikhislamov [et al.] // Astrophys. J. - 2018. - Vol. 866, Is. 1. - Ст. 47, DOI 10.3847/1538-4357/aadf39. - Cited References:48. - This work was supported by grant No. 18-12-00080 of the Russian Science Foundation. H.L., L.F., N.D., M.G., K.G.K., C.P.J. acknowledge the Austrian Science Foundation (FWF) project I2939-N27, FWF-NFN projects S11606-N16, WS11607-N16 and S11604-N16. M.L.K. also acknowledges the FWF projects P25587-N27, P25640-N27 and Leverhulme Trust grant IN-2014-016. Parallel computing simulations, key for this study, have been performed at Computation Center of Novosibirsk State University, SB RAS Siberian Supercomputer Center, and Supercomputing Center of the Lomonosov Moscow State University. . - ISSN 0004-637X. - ISSN 1538-4357РУБ Astronomy & Astrophysics

Аннотация: The absorption of stellar radiation observed by HD 209458b in the resonant lines of O I and C II has not yet been satisfactorily explained. We apply a 2D hydrodynamic multi-fluid model that self-consistently describes the expanding planetary wind, driven by stellar XUV radiation and influenced by tidal forces and the surrounding stellar wind. According to this model, HD 209458b has a hydrogen-dominated plasmasphere, expanding beyond the Roche lobe, in the form of two supersonic streams that propagate toward and away from the star. The species heavier than hydrogen and helium are dragged in the escaping material streams and accelerated up to 50 km s(-1). Our simulations show that, assuming solar abundances, O I and C II produce absorption due to the Doppler resonance mechanism at the level of 6%-10%, which is consistent with the observations. Most of this absorption takes place in the streams. The transit depth in the O I and C II lines is unaffected by the stellar wind, unless it is strong enough to form a compact bowshock around the planet and able to redirect all the escaping material to the tail. In this case, the absorption profile becomes asymmetric due to the prominent blueshifted attenuation. Thus, the spectroscopic measurements enable probing of the planetary wind character, as well as the strength of the stellar wind. The computed absorption at wavelengths of the Si III, Mg I, and Mg II lines at solar abundances appears to be much stronger, compared to the observations. This possibly indicates that Si and Mg may be under-abundant in the upper atmosphere of HD 209458b.

WOS,
Смотреть статью,
Scopus

Держатели документа:
Inst Laser Phys SB RAS, Novosibirsk, Russia.
Austrian Acad Sci, Space Res Inst, Graz, Austria.
Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia.
Univ Vienna, Dept Astrophys, Vienna, Austria.
Inst Computat Modelling SB RAS, Krasnoyarsk, Russia.
Siberian Fed Univ, Polytech Inst, Krasnoyarsk, Russia.

Доп.точки доступа:
Shaikhislamov, I. F.; Khodachenko, M. L.; Lammer, H.; Fossati, L.; Dwivedi, N.; Gudel, M.; Kislyakova, K. G.; Johnstone, C. P.; Berezutsky, A. G.; Miroshnichenko, I. B.; Posukh, V. G.; Erkaev, N., V; Ivanov, V. A.; Russian Science Foundation [18-12-00080]; Austrian Science Foundation (FWF) [I2939-N27]; FWF-NFN projects [S11606-N16, WS11607-N16, S11604-N16]; FWF [P25587-N27, P25640-N27]; Leverhulme Trust [IN-2014-016]