 |
| Titel |
The superthermal ion environment near comet 67P/Churyumov-Gerasimenko at low activity |
| VerfasserIn |
Hans Nilsson, Gabriella Stenberg Wieser, Etienne Behar, Masatoshi Yamauchi, Cyril Simon Wedlund, Esa Kallio, Jim Burch, Chris Carr, Anders Eriksson, Karl-Heinz Glassmeier, Jean-Pierre Lebreton, Pierre Henri, Herbert Gunell |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109752
|
| Publikation (Nr.) |
 EGU/EGU2015-9687.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Rosetta mission has been designed to rendezvous with and escort comet
67P/Churyumov-Gerasimenko from a heliocentric distance ofÂ>3.6 AU, when the comet still
has a low activity level, until perihelion passage at 1.25 AU where the comet reaches the
maximum of its activity. Initially, the solar wind permeates the thin comet atmosphere that
has just begun to form from sublimation. Eventually the size and plasma pressure of the
ionizedÂatmosphere leads to the formation ofÂplasma boundaries: a magnetosphere is
born.ÂUsing the Rosetta Plasma Consortium Ion Composition Analyzer, we study the
gradual evolution from theÂfirst detectable traces of water ions to the stage where the comet
atmosphere starts to repelÂthe solar wind at a distance from the sun of about 3.3 AU.
Gradually the mass loading caused by picked-up comet ions starts to deflect the solar wind.
Charge exchange between the solar wind and comet atmosphere gradually increases with
comet activity, leading to a situation where a significant fraction of the solar wind has
charge-exchanged close to the comet nucleus. Pick up ions created upstream of the comet
nucleus are accelerated by the solar wind electric field and are seen with energies up
to about 1 keV as they move back towards the nucleus. Locally produced water
ions are seen moving with velocities similar to the neutral outgassing velocity of
the order of 1 km/s (Â10 eV), but with their direction and speed influenced by the
solar wind electric field. High charge state solar wind ions (O6+, O5+) are also
seen at times. We quantify the super thermal ion environment near a low activity
comet and show how it depends on the solar wind intensity and the distance to the
sun. |
|
|
|
|
|
|