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Energetic neutral atoms around HD 209458b: estimations of magnetospheric properties
Swedish Institute of Space Physics, P.O. Box 812, SE-98128 Kiruna, Sweden.
Swedish Institute of Space Physics, P.O. Box 812, SE-98128 Kiruna, Sweden.
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2010 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 709, no 2, 670-679 p.Article in journal (Refereed) Published
Abstract [en]

HD 209458b is an exoplanet found to transit the disk of its parent star. Observations have shown a broad absorption signature about the Ly alpha stellar line during transit, suggesting the presence of a thick cloud of atomic hydrogen around the "hot Jupiter" HD 209458b. This work expands on an earlier work studying the production of energetic neutral atoms (ENAs) as a result of the interaction between the stellar wind and the exosphere. We present an improved flow model of HD 209458b and use stellar wind values similar to those in our solar system. We find that the ENA production is high enough to explain the observations, and we show that-using expected values for the stellar wind and exosphere-the spatial and velocity distributions of ENAs would give absorption in good agreement with the observations. We also study how the production of ENAs depends on the exospheric parameters and establish an upper limit for the obstacle standoff distance at approximately 4-10 planetary radii. Finally, we compare the results obtained for the obstacle standoff distance with existing exomagnetospheric models and show how the magnetic moment of HD 209458b can be estimated from ENA observations.

Place, publisher, year, edition, pages
Bristol: Institute of Physics (IOP), 2010. Vol. 709, no 2, 670-679 p.
Keyword [en]
methods, data analysis, methods, numerical, stars, winds, outflows
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:umu:diva-3360DOI: 10.1088/0004-637X/709/2/670ISI: 000273579800010OAI: oai:DiVA.org:umu-3360DiVA: diva2:142027
Available from: 2008-09-04 Created: 2008-09-04 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Numerical modelling of ENAs from stellar wind interactions
Open this publication in new window or tab >>Numerical modelling of ENAs from stellar wind interactions
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energetic neutral atoms (ENAs) are produced whenever a stellar wind encounters a neutral atmosphere. If a stellar wind proton comes sufficiently close to a neutral a charge-exchange reaction may take place, transforming the proton into an ENA. Unaffected by magnetic and electric fields, ENAs provide an opportunity for global imaging of stellar wind interactions.

This thesis presents methods and results of numerical modelling of stellar wind interactions. In particular it treats in depth production of ENAs at comets, Mars and the extrasolar planet HD 209458b.

Sufficiently accurate numerical models of stellar wind interactions require extensive computations. Parallel computing has therefore been used throughout the work, both for fluid and particle simulations of space plasmas. This thesis describes the use of a general simulation tool, providing parallel computing for space plasma simulations.

The thesis presents estimations of the magnitude and morphology of the ENA production at comets and HD 209458b. It compares the results obtained with observations and analyzes them in the light of ENA production at similar objects. Also, simulated ENA images for Mars were produced and compared to observations.

Place, publisher, year, edition, pages
Kiruna: Institutet för rymdfysik (IRF), 2008. 52 p.
Series
IRF Scientific Report, ISSN 0284-1703 ; 297
Keyword
Space physics, Space technology, Astrophysics
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:umu:diva-1804 (URN)978-91-977255-5-2 (ISBN)
Public defence
2008-09-26, Aulan, Institutet för rymdfysik, Etian 100, Kiruna, 10:00
Opponent
Supervisors
Available from: 2008-09-04 Created: 2008-09-03Bibliographically approved

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