Seminars of the Focus Area Complex Systems

Prof. Dr. C. Beta, Prof. Dr. K. Dethloff, Prof. Dr. R. Engbert, Prof. Dr. M. Holschneider, Prof. Dr. W. Huisinga, Prof. Dr. Ralf Metzler, Prof. Dr. A. Pikovsky, Prof. Dr. S. Reich, Prof. Dr. M. Rosenblum, Prof. Dr. G. Rüdiger, Prof. Dr. T. Scheffer, Prof. Dr. F. Scherbaum, Prof. Dr. J. Selbig, Prof. Dr. F. Spahn

Seminar

Speaker: Larry Esposito, Laboratory for Atmosphere and Space Physics (LASP), Univ. Colorado

Title: Non-Linear Dynamics of Saturn's Rings * Kolloquium des Instituts für Physik und Astronomie

Time: Wed, Jul 5, 2017, 16:15am

Place: bldg 28, room 0.108

Abstract:
They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description is needed. Stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium.

1) They are strongly forced by resonances: which drive a non-linear response, and push the system across thresholds that lead to persistent states.

2) Periodic forcing from the moon causes streamline crowding, downstream from the forcing and outside of the resonance; Collisions damp the relative velocity. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average. Aggregates that form are thus out of phase with the moon forcing. These can tear apart the ring material downstream. Solitary Waves: Created when Janus moves inward every 8 years, they move through the density waves. Maintaining their morphology requires a dispersion relation that depends on amplitude.Ring Structure: Gaps explain the azimuthal brightness variations, indicating 'self-gravity wakes'. These are found between the strong density wave crests. Rapid growth implies Disk Instability. Binary accretion and sweep up is too slow to create the structures seen in occultation statistics and blotchy structure that have time scales of an orbital period. F ring kittens: Show a broken power-law size distribution, and are found preferentially opposite the shepherd moons.

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Past NLD Seminars (1994-2007) & (2008 ...)

Students' seminar: Theoretical Physics, PIK, Modeling & TSA Berlin-Potsdam-Colloquia: PhysGesellschaft Berlin, TU Berlin, Pro Physik, AIP, AEI, MPI-KGF, GFZ, HMI, PIK, AWI, Max Planck Institute for the History of Science, Mathematik, DPG Disputationen, & Vorschau UP

Udo Schwarz, Zentrum für Dynamik komplexer Systeme,
Universität Potsdam, Campus Golm Karl-Liebknecht-Str. 24, 14476 Potsdam, building 28, room 2.107
Phone: (+49-331) 977-1658, Fax : (+49-331) 977-1045

Email: Udo.Schwarz AT uni-potsdam.de

DFG SFB 1294

DFG Sonderforschungsbereich 1294 Data assimilation

DFG SPP 1488

DFG Schwerpunktprogramm 1488 Planetmag


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