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

Autor(en)

Kristina Kislyakova, Colin Johnstone, Petra Odert, Theresa Rank-Lüftinger, Manuel Güdel, N V Erkaev, Helmut Lammer, Mats Holmström, Maxim L. Khodachenko

Abstrakt

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 1D 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 ∼6.4 × 10

³⁰ s

^-1 and ∼4.1 × 10

³¹ s

^-1, depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ∼1.07 × 10

⁷ g s

^-1 and ∼6.8 × 10

⁷ g s

^-1 respectively, which is a few percent of the thermal escape rates.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Karl-Franzens-Universität Graz, Österreichische Akademie der Wissenschaften (ÖAW), Siberian Federal University, Swedish Institute of Space Physics, Lomonosov Moscow State University (MSU), Russian Academy of Sciences

Journal

Astronomy & Astrophysics

Band

562

Anzahl der Seiten

8

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201322933

Publikationsdatum

02-2014

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie, 103004 Astrophysik

Schlagwörter

ASJC Scopus Sachgebiete

Astronomy and Astrophysics, Space and Planetary Science

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/305c5f9f-9912-49c1-8a75-1c5576254377