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| Titel |
Mars Express measurements of the ion escape rate for solar minimum |
| VerfasserIn |
Andrey Fedorov, Stas Barabash, Jean-André Sauvaud, Rickard Lundin |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051818
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| Zusammenfassung |
| The Mars’ atmosphere escape due to the interaction with the solar wind is thought to be an
important channel of the atmospheric gases loss. Particle escape is produced by several
physical mechanisms of ion acceleration in the planet induced magnetosphere. The escaping
ion distribution is controlled by the convective electric field and strongly variable and
inhomogeneous in the time and space domains that makes calculations of the global escape
rates (particle-sec) from the microscopic and instantaneous in situ measurements (time and
space dependent differential flux) a very complex problem. To correctly calculate the rates we
showed that the escape rates calculated in both the planet-related and electric-field-related
frames are about the same, provided the orbital sampling is sufficiently dense and
homogeneous in the electric-field related frame. We proved this criteria for a limited set of
orbits where the electric-field-related frame can be reconstructed and used the whole data set
to obtain the global escape rate. To properly take into account the limited instrument’s filed
of view we used the epoch superposition method. To correctly deal with the low
energy part of the distribution function (1 - 10 eV) affected by unknown spacecraft
potential we extrapolated the measurements from the range 10 eV - 30 eV down to the
oxygen escape energy. We applied the developed method to two years of the Mars
Express ion measurements over the period from May 20, 2007 to May 20, 2009
corresponding to the minimum solar activity. The paper provides the total escape rate of the
heavy ions of planetary origin in the solar minimum and discuss the acceleration
mechanisms. |
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