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[Text] / A. Divin [et al.] // Phys. Plasmas. - 2010. - Vol. 17, Is. 12. - Ст. 122102, DOI 10.1063/1.3521576. - Cited References: 42. - The present work is supported partially by the Onderzoekfonds KU Leuven (Research Fund KU Leuven) and by the European Commission's Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 218816 (SOTERIA project, www.soteria- space.eu). Additional support is provided by RFBR (Grant No. 09-05-91000-ANF-a). V.S.S. thanks ISSI for hospitality and financial support. The simulations were conducted on the resources of the Vlaams Supercomputer Centrum (VSC) at the Katholieke Universiteit Leuven. . - ISSN 1070-664XРУБ Physics, Fluids & Plasmas

Аннотация: A new model of the electron pressure anisotropy in the electron diffusion region in collisionless magnetic reconnection is presented for the case of antiparallel configuration of magnetic fields. The plasma anisotropy is investigated as source of collisionless dissipation. By separating electrons in the vicinity of the neutral line into two broad classes of inflowing and accelerating populations, it is possible to derive a simple closure for the off-diagonal electron pressure component. The appearance of these two electron populations near the neutral line is responsible for the anisotropy and collisionless dissipation in the magnetic reconnection. Particle-in-cell simulations verify the proposed model, confirming first the presence of two particle populations and second the analytical results for the off-diagonal electron pressure component. Furthermore, test-particle calculations are performed to compare our approach with the model of electron pressure anisotropy in the inner electron diffusion region by Fujimoto and Sydora [Phys. Plasmas 16, 112309 (2009)]. (C) 2010 American Institute of Physics. [doi:10.1063/1.3521576]


Доп.точки доступа:
Divin, A.; Markidis, S.; Lapenta, G.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.

[Text] / H. . Lammer [et al.] // Astron. Astrophys. - 2009. - Vol. 506, Is. 1. - P399-410, DOI 10.1051/0004-6361/200911922. - Cited References: 46. - The authors thank the anonymous referee for constructive comments and suggestions which helped to improve the paper. H. Lammer, P. Odert, M. Leitzinger, M. L. Khodachenko and A. Hanslmeier gratefully acknowledge the Austrian Fonds zur Forderung der wissenschaftlichen Forschung (FWF grant P19446) for supporting this project. M. Panchenko and M. L. Khodachenko acknowledge also the Austrian Fonds zur Forderung der wissenschaftlichen Forschung (project P20680-N16). H. Lammer, H. I. M. Lichtenegger, H. K. Biernat, Yu. N. Kulikov and N. V. Erkaev thank the AAS "Verwaltungsstelle fur Auslandsbeziehungen" and the RAS. H. Lammer, H. I. M. Lichtenegger, M. L. Khodachenko and Yu. N. Kulikov acknowledge support from the Helmholtz-Gemeinschaft as this research has been supported by the Helmholtz Association through the research alliance "Planetary Evolution and Life". H. Lammer, M. L. Khodachenko, T. Penz, and Yu. N. Kulikov also acknowledge the International Space Science Institute (ISSI; Bern, Switzerland) and the ISSI teams "Evolution of Habitable Planets" and "Evolution of Exoplanet Atmospheres and their Characterization". H. K. Biernat acknowledges additional support due to the Austrian Science Fund under project P20145-N16. The authors also acknowledge fruitful discussions during various meetings related to the Europlanet N2 activities as well as within the N2 Exoplanet discipline working group DWG 7. T. Penz and G. Micela acknowledge support by the Marie Curie Fellowship Contract No. MTKD-CT-2004-002769 of the project "The influence of stellar high radiation on planetary atmospheres". The authors also thank the Austrian Ministry bm:bwk and ASA for funding the CoRoT project. . - ISSN 0004-6361РУБ Astronomy & Astrophysics

Аннотация: Aims. We study the possible atmospheric mass loss from 57 known transiting exoplanets around F, G, K, and M-type stars over evolutionary timescales. For stellar wind induced mass loss studies, we estimate the position of the pressure balance boundary between Coronal Mass Ejection (CME) and stellar wind ram pressures and the planetary ionosphere pressure for non- or weakly magnetized gas giants at close orbits. Methods. The thermal mass loss of atomic hydrogen is calculated by a mass loss equation where we consider a realistic heating efficiency, a radius-scaling law and a mass loss enhancement factor due to stellar tidal forces. The model takes into account the temporal evolution of the stellar EUV flux by applying power laws for F, G, K, and M-type stars. The planetary ionopause obstacle, which is an important factor for ion pick-up escape from non- or weakly magnetized gas giants is estimated by applying empirical power-laws. Results. By assuming a realistic heating efficiency of about 10-25% we found that WASP-12b may have lost about 6-12% of its mass during its lifetime. A few transiting low density gas giants at similar orbital location, like WASP-13b, WASP-15b, CoRoT-1b or CoRoT-5b may have lost up to 1-4% of their initial mass. All other transiting exoplanets in our sample experience negligible thermal loss (<= 1%) during their lifetime. We found that the ionospheric pressure can balance the impinging dense stellar wind and average CME plasma flows at distances which are above the visual radius of "Hot Jupiters", resulting in mass losses <2% over evolutionary timescales. The ram pressure of fast CMEs cannot be balanced by the ionospheric plasma pressure for orbital distances between 0.02-0.1 AU. Therefore, collisions of fast CMEs with hot gas giants should result in large atmospheric losses which may influence the mass evolution of gas giants with masses
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Доп.точки доступа:
Lammer, H.; Odert, P.; Leitzinger, M.; Khodachenko, M.L.; Panchenko, M.; Kulikov, Y.N.; Zhang, T.L.; Lichtenegger, H.I.M.; Erkaev, N.V.; Еркаев, Николай Васильевич; Wuchterl, G.; Micela, G.; Penz, T.; Biernat, H.K.; Weingrill, J.; Steller, M.; Ottacher, H.; Hasiba, J.; Hanslmeier, A.; Austrian Fonds zur Forderung der wissenschaftlichen Forschung [P19446, P20680-N16]; Helmholtz Association; Austrian Science Fund [P20145-N16]; "The influence of stellar high radiation on planetary atmospheres" [MTKD-CT-2004-002769]

[Text] / D. B. Korovinskiy [et al.] // J. Geophys. Res-Space Phys. - 2011. - Vol. 116. - Ст. A05219, DOI 10.1029/2010JA015942. - Cited References: 45. - This work is supported by the Austrian Science Fund under projects I193-N16 and P21051-N16, by RFBR grant 09-05-91000-ANF-a, and by SPSU grant 11.38.47.2011. V. S. Semenov also thanks ISSI for hospitality and financial support. . - ISSN 2169-9380РУБ Astronomy & Astrophysics

Аннотация: A 2.5-D analytical electron Hall magnetohydrodynamic model of steady state magnetic reconnection in a collisionless compressible plasma with a constant electron temperature is developed. It is shown that as in the incompressible case, the solution of the Grad-Shafranov equation for the magnetic potential is a basis for the problem analysis. The formation of the double electric layers and layers of low-density plasma, mapping the magnetic separatrices, are investigated. It is found that the formation of depletion layers should not be governed by the out-of-plane magnetic field, but rather, the origin of these layers lies inside the electron diffusion region. The double electric layers are found to be thin separatrices-elongated sheets, whose cross sections are of the order of the electron diffusion region half width. These charged layers provide the presence of the strong electric field orthogonal to the in-plane projection of the magnetic field, which forces electrons to accelerate into the out-of-plane direction. Outside of the double electric layers, the condition of quasi-neutrality of the plasma is found to be fulfilled to high accuracy.


Доп.точки доступа:
Korovinskiy, D.B.; Semenov, V.S.; Erkaev, N.V.; Еркаев, Николай Васильевич; Divin, A.V.; Biernat, H.K.; Mostl, U.V.

[Text] / H. . Lammer [et al.] // Mon. Not. Roy. Astron. Soc. - 2014. - Vol. 439, Is. 4. - P. 3225-3238, DOI 10.1093/mnras/stu085. - Cited References: 75. - The authors acknowledge the support by the FWF NFN project S11601-N16 'Pathways to Habitability: From Disks to Active Stars, Planets and Life', and the related FWF NFN subprojects, S 116 02-N16 'Hydrodynamics in Young Star-Disk Systems', S116 604-N16 'Radiation & Wind Evolution from T Tauri Phase to ZAMS and Beyond', and S116607-N16 'Particle/Radiative Interactions with Upper Atmospheres of Planetary Bodies Under Extreme Stellar Conditions'. KGK, YNK, HL, and PO thank also the Helmholtz Alliance project 'Planetary Evolution and Life'. ML and PO acknowledge support from the FWF project P22950-N16. NVE acknowledges support by the RFBR grant no. 12-05-00152-a. Finally, the authors thank the International Space Science Institute (ISSI) in Bern, and the ISSI team 'Characterizing stellar-and exoplanetary environments'. . - ISSN 0035-8711. - ISSN 1365-2966РУБ Astronomy & Astrophysics

Аннотация: We investigate the origin and loss of captured hydrogen envelopes from protoplanets having masses in a range between 'sub-Earth'-like bodies of 0.1 M-circle plus and 'super-Earths' with 5 M-circle plus in the habitable zone at 1 au of a Sun-like G star, assuming that their rocky cores had formed before the nebula gas dissipated. We model the gravitational attraction and accumulation of nebula gas around a planet's core as a function of protoplanetary luminosity during accretion and calculate the resulting surface temperature by solving the hydrostatic structure equations for the protoplanetary nebula. Depending on nebular properties, such as the dust grain depletion factor, planetesimal accretion rates, and resulting luminosities, for planetary bodies of 0.1-1 M-circle plus we obtain hydrogen envelopes with masses between similar to 2.5 x 10(19) and 1.5 x 10(26) g. For 'super-Earths' with masses between 2 and 5 M-circle plus more massive hydrogen envelopes within the mass range of similar to 7.5 x 10(23)-1.5 x 10(28) g can be captured from the nebula. For studying the escape of these accumulated hydrogen-dominated protoatmospheres, we apply a hydrodynamic upper atmosphere model and calculate the loss rates due to the heating by the high soft-X-ray and extreme ultraviolet (XUV) flux of the young Sun/star. The results of our study indicate that under most nebula conditions 'sub-Earth' and Earth-mass planets can lose their captured hydrogen envelopes by thermal escape during the first similar to 100 Myr after the disc dissipated. However, if a nebula has a low dust depletion factor or low accretion rates resulting in low protoplanetary luminosities, it is possible that even protoplanets with Earth-mass cores may keep their hydrogen envelopes during their whole lifetime. In contrast to lower mass protoplanets, more massive 'super-Earths', which can accumulate a huge amount of nebula gas, lose only tiny fractions of their primordial hydrogen envelopes. Our results agree with the fact that Venus, Earth, and Mars are not surrounded by dense hydrogen envelopes, as well as with the recent discoveries of low density 'super-Earths' that most likely could not get rid of their dense protoatmospheres.

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ИВМ СО РАН

Доп.точки доступа:
Lammer, H.; Stokl, A.; Erkaev, N.V.; Еркаев, Николай Васильевич; Dorfi, E.A.; Odert, P.; Gudel, M.; Kulikov, Y.N.; Kislyakova, K.G.; Leitzinger, M.; FWF NFN [S11601-N16, S 116 02-N16, S116 604-N16, S116607-N16]; FWF [P22950-N16]; RFBR [12-05-00152-a]