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The tailward flow of energetic neutral atoms observed at Mars
Institutet för rymdfysik (IRF).
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2008 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, E12012Article in journal (Refereed) Published
Abstract [en]

The ASPERA-3 experiment on Mars Express provides the first measurements of energetic neutral atoms (ENAs) from Mars. These measurements are used to study the global structure of the interaction of the solar wind with the Martian atmosphere. In this study we describe the tailward ENA flow observed at the nightside of Mars. After characterizing energy spectra of hydrogen ENA signals, we present composite images of the ENA intensities and compare them to theoretical predictions (empirical and MHD models). We find that the tailward flow of hydrogen ENAs is mainly generated by shocked solar wind protons. Despite intensive search, no oxygen ENAs above the instrument threshold are detected. The results challenge existing plasma models and constrain the hydrogen exospheric densities and atmospheric hydrogen and oxygen loss rates at low solar activity.

Place, publisher, year, edition, pages
Washington: American Geophysical Union (AGU), 2008. Vol. 113, E12012
Keyword [en]
solar-wind interaction, subsolar ENA jet, 1st-ENA observations, Aspera-3 observations, upper atmosphere, charge-exchange, express mission, space plasmas, hydrogen, distributions
National Category
Geochemistry Geophysics
Identifiers
URN: urn:nbn:se:umu:diva-3361DOI: 10.1029/2008JE003139ISI: 000262043600001OAI: oai:DiVA.org:umu-3361DiVA: diva2:142028
Available from: 2008-09-04 Created: 2008-09-04 Last updated: 2017-10-10Bibliographically 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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