 |
| Titel |
3-D Simulations of the Inner Dust Comae for Comet 67P/Churyumov-Gerasimenko |
| VerfasserIn |
Raphael Marschall, Ying Liao, Cheng-Chin Su, Jong-Shinn Wu, Nicolas Thomas, Martin Rubin, Ian Lin Lai, Wing-Huen Ip, Horst Uwe Keller, Jörg Knollenberg, Ekkehard Kührt, Yuri Skorov, Kathrin Altwegg  , Jean-Baptiste Vincent, Adeline Gicquel, Xian Shi, Holger Sierks, Giampiero Naletto |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112525
|
| Publikation (Nr.) |
 EGU/EGU2015-12685.pdf |
|
|
|
|
|
| Zusammenfassung |
| The aims of this study are to (1) model the gas flow-field in the innermost coma for a
plausible activity distributions of ROSETTA’s target comet 67P/Churyumov-Gerasimenko
(67P) using the SHAP2 model, (2) compare this with the ROSINA/COPS gas density (3)
investigate the acceleration of dust by gas drag and the resulting dust distribution, (4) produce
artificial images of the dust coma brightness as seen from different viewing geometries for a
range of heliocentric distances and (5) compare the artificial images quantitatively with
observations by the OSIRIS imaging system.
We calculate the dust distribution in the coma within the first ten kilometers of the
nucleus by assuming the dust to be spherical test particles in the gas field without any back
coupling. The motion of the dust is driven by the drag force resulting from the gas flow. We
assume a quadratic drag force with a velocity and temperature-dependent drag coefficient.
The gravitational force of a point nucleus on the dust is also taken into account which
will e.g. determine the maximal liftable size of the dust. Surface cohesion is not
included.
40 dust sizes in the range between 8 nm and 0.3 mm are considered. For every dust
size the dust densities and velocities are calculated by tracking around one million
simulation particles in the gas field. We assume the distribution of dust according to size
follows a power law, specifically the number of particles n or a particular radius r is
specified by n ~ r-β with usual values of 3 ≈¤ β ≈¤ 4 where β = 3 corresponds to
the case of equal mass per size and β = 4 to a shift of the mass towards the small
particles.
For the comparison with images of the high resolution camera OSIRIS on board ESAs
ROSETTA spacecraft the viewing geometry of the camera can be specified and a line of sight
integration through the dust density is performed. By means of Mie scattering on the particles
the dust brightness can be determined.
A variety of dust size distributions, gas to dust mass ratios, wavelengths and optical
properties can thus be studied and compared with the data. |
|
|
|
|
|
|