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| Titel |
Revisiting Cometary Bow Shock Positions |
| VerfasserIn |
C. Koenders, K.-H. Glassmeier, C. Nabert, I. Richter |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063389
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| Zusammenfassung |
| The interaction region between the exosphere of a comet and the solar wind reveals a variety
of plasma structures and boundaries which are predicted by several plasma models and/or
have been observed by a spacecraft mission, e.g. by the GIOTTO mission to comet 1P/Halley
and 26P/Grigg-Skjellerup. With regard to the arrival of the next cometary spacecraft mission
ROSETTA at its target comet 67P/Churyumov-Gerasimenko (CG), it is necessary to develop
models of the estimated positions of the different plasma boundaries. This knowledge will be
used for the mission planning of the ROSETTA mission in order to prepare the required
trajectories for the measurements, to ensure the scientific success of this unique
mission.
One of the boundaries in the interaction region, which is of particular interest for the
mission planning, is the bow shock, where the supersonic flow is strongly decelerated to
subsonic velocities. This boundary has been first predicted by Biermann et al. [1967]. They
used a one-dimensional hydrodynamical model to describe the plasma flow in front of the
bow shock. As a result, they ascertained that the velocity of the plasma decreases during the
injection of mass into the flow. Furthermore, they found a point at which the mean
molecular weight of the plasma normalised by proton mass reaches the critical value of
4/3. Hence, Biermann et al. [1967] suggested that the bow shock is located at this
position. For typical solar wind conditions at 1.3 AU and a gas production rate
of 5-
1027 1/s this point would be 5557 km in front of comet CG. However,
more recent numerical simulation results of Hansen et al. [2007] and Gortsas et al.
[2010] for the same set of parameters forecast distances of 3500 km and 1764 km,
respectively.
Using the A.I.K.E.F. hybrid code, we present detailed further simulations and
determinations of the bow shock stand-off distance. Deviations from the earlier results by
Biermann et al. [1967] are discussed and explained. |
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