TY  - JOUR
A1  - Hoffmann, Holger
A1  - Seiss, Martin
A1  - Salo, Heikki
A1  - Spahn, Frank
T1  - Vertical structures induced by embedded moonlets in Saturn's rings
JF  - Icarus : international journal of solar system studies
N2  - We study the vertical extent of propeller structures in Saturn's rings (i) by extending the model of Spahn and Sremcevic (Spahn, F., Sremcevic, M. [2000]. Astron. Astrophys., 358, 368-372) to include the vertical direction and (ii) by performing N-body box simulations of a perturbing moonlet embedded into the rings. We find that the gravitational interaction of ring particles with a non-inclined moonlet does not induce considerable vertical excursions of ring particles, but causes a considerable thermal motion in the ring plane. We expect ring particle collisions to partly convert the lateral induced thermal motion into vertical excursions of ring particles in the course of a quasi-thermalization. The N-body box simulations lead to maximal propeller heights of about 0.6-0.8 Hill radii of the embedded perturbing moonlet. Moonlet sizes estimated by this relation are in good agreement with size estimates from radial propeller scalings for the propellers Bleriot and Earhart. For large propellers, the extended hydrodynamical propeller model predicts an exponential propeller height relaxation, confirmed by N-body box simulations of non-self gravitating ring particles. Exponential cooling constants, calculated from the hydrodynamical propeller model agree fairly well with values from fits to the tail of the azimuthal height decay of the N-body box simulations. From exponential cooling constants, determined from shadows cast by the propeller Earhart and imaged by the Cassini spacecraft, we estimate collision frequencies of about 6 collisions per particle per orbit in the propeller gap region and about 11 collisions per particle per orbit in the propeller wake region. (C) 2015 Elsevier Inc. All rights reserved.
KW  - Planetary rings
KW  - Saturn, rings
KW  - Saturn, satellites
KW  - Disks
Y1  - 2015
U6  - https://doi.org/10.1016/j.icarus.2015.02.003
SN  - 0019-1035
SN  - 1090-2643
VL  - 252
SP  - 400
EP  - 414
PB  - Elsevier
CY  - San Diego
ER  -