Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

Тип публикации: статья из журнала

Год издания: 2014

Идентификатор DOI: 10.1051/0004-6361/201322933

Ключевые слова: planet-star interactions, planets and satellites: atmospheres, planets and satellites: individual: Kepler-11 system, methods: numerical

Аннотация: Aims. We study the interactions between stellar winds and the extended hydrogen-dominated upper atmospheres of planets. We estimate the resulting escape of planetary pick-up ions from the five "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Methods. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic ID hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a direct simulation Monte Carlo model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model, we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions, and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and the thermal escape rates of the neutral planetary hydrogen atoms. Results. Our results show that a huge neutral hydrogen corona is formed around the planet for all Kepler-11b-f exoplanets. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between similar to.6.4x10(30) s(-1) and similar to 4.1 x10(31) s(-1), depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of similar to 1.07 x 10(7) g s(-1) and similar to 6.8 x 10(2) g s(-1) respectively, which is a few percent of the thermal escape rates.

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Издание

Журнал: ASTRONOMY & ASTROPHYSICS

Выпуск журнала: Vol. 562

ISSN журнала: 14320746

Место издания: LES ULIS CEDEX A

Издатель: EDP SCIENCES S A

Авторы

  • Kislyakova K.G. (Space Research Institute,Austrian Academy of Sciences)
  • Odert P. (Institute of Physics,University of Graz)
  • Lammer H. (Space Research Institute,Austrian Academy of Sciences)
  • Khodachenko M.L. (Institute of Nuclear Physics,Moscow State University)
  • Johnstone C.P. (University of Vienna,Department of Astrophysics)
  • Luftinger T. (University of Vienna,Department of Astrophysics)
  • Gudel M. (University of Vienna,Department of Astrophysics)
  • Erkaev N.V. (Siberian Federal University)
  • Holmstrom M. (Swedish Institute of Space Physics)

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