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Titel |
Ion transport in the upper ionospheres of Mars and Venus |
VerfasserIn |
M. Franz, E. Dubinin, E. Nielsen, A. Angsmann, J. Woch, S. Barabash, R. Lundin, A. Fedorov |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250023347
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Zusammenfassung |
The upper ionospheres of Mars and Venus are permeated by the magnetic fields
induced by the solar wind. It is a long-standing question wether these fields can put
the dense ionospheric plasma into motion. If so, the cross-terminator flow of the
upper ionosphere could explain a significant part of the ion escape from the planets
atmospheres. But it has been technically very challenging to measure the ion flow at
energies below 20eV. The only such measurements have been made by the ORPA
instrument of the Pioneer Venus Orbiter reporting speeds of 1-5km/s for O+ ions at
Venus above 300km altitude at the terminator (Knudsen et al, GRL 1982). Since
these observations could never be confirmed by other instruments they have been
debated. We here report on new measurements of the cross-terminator ion flow by the
ASPERA 3 and 4 experiments onboard Mars and Venus Express with support from
the MARSIS radar experiment which confirm O+ flow speeds of around 6km/s
with fluxes of 1.2 ⋅ 109/cm2s (for Mars). We discuss the implication of these new
observation for ion escape and possible extensions of the analysis to dayside observations
which might allow us to infer the flow structure imposed by the induced magnetic
field. |
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