| 日時: | 2011 年 11 月 4 日(金) 10:45-11:30 |
| 場所: | CPS セミナー室 |
| 講演者: | Heikki Salo (オウル大学) |
| 世話人: | 大槻 圭史 |
| タイトル: | Dynamical and photometric modeling of Saturn's Rings |
| abstract: |
Saturn's rings, with their extremely rich multi-scale structure, offer an ideal laboratory for studies of gravitational dynamics and collective viscous behavior in nonlinear systems. In addition, their observable photometric characteristics provide stringent constraints for the physical properties of individual, unseen particles. To facilitate such studies, I use a combination of dynamical N-body simulations and photometric Monte Carlo ray tracing. An important diagnostic for the local velocity dispersion in rings is provided by the long-studied azimuthal brightness variations in both the A and the inner B ring. The non-axisymmetric gravity wakes provide a natural explanation for these observation, indicating that the ring is close to threshold of gravitational instability. Such wakes also imply longitude-dependence of ring optical depth, as verified by Cassini RSS, UVIS, and VIMS occultations. The properties of gravity wakes can be used to probe the particles' physical properties like coefficient of restitution and internal density. Besides wakes, the overall photometric properties (dependence of ring brightness on elevation and phase angle) constrain the vertical distribution and volume filling factor of the system, as well as the particle size distribution. |
| キーワード: | リング、カッシーニ、微細構造 |