TY  - JOUR
A1  - Spahn, Frank
A1  - Krivov, Alexander V.
A1  - Sremcevic, Miodrag
A1  - Schwarz, U.
A1  - Kurths, Jürgen
T1  - Stochastic forces in circumplanetary dust dynamics
N2  - Charged dust grains in circumplanetary environments experience, beyond various deterministic forces, also stochastic perturbations caused, by fluctuations of the magnetic field, the charge of the grains, by chaotic rotation of aspherical grains, etc. Here we investigate the dynamics of a dust population in a circular orbit around a planet which is perturbed by a stochastic planetary magnetic field B', modeled by an isotropically Gaussian white noise. The resulting perturbation equations give rise to a modified diffusion of the inclinations i and eccentricities e. The diffusion coefficient is found to be D proportional to w^2 O /n^2 , where the gyrofrequency, the Kepler frequency, and the synodic frequency are denoted by w , O, and n, respectively. This behavior has been checked against numerical simulations. We have chosen dust grains (1 m in radius) ejected from Jupiter's satellite Europa in circular equatorial orbits around Jupiter and integrated numerically their trajectories over their typical lifetimes (100 years). The particles were exposed to a Gaussian fluctuating magnetic field B' with the same statistical properties as in the analytical treatment. These simulations have confirmed the analytical results. The theoretical studies showed the statistical properties of B' to be of decisive importance. To estimate them, we analyzed the magnetic field data obtained by the Galileo spacecraft magnetometer at Jupiter and found almost Gaussian fluctuations of about 5% of the mean field and exponentially decaying correlations. This results in a diffusion of orbital inclinations and eccentricities of the dust grains of about ten percent over the lifetime of the particles. For smaller dusty motes or for close-in particles (e.g., in Jovian gossamer rings) stochastics might well dominate the dynamics.
Y1  - 2003
UR  - http://www.agu.org/pubs/current/je/
ER  - 
TY  - JOUR
A1  - Schwarz, Udo
A1  - Kurths, Jürgen
A1  - Spahn, Frank
A1  - Petzschmann, Olaf
T1  - Reply on the comment of "Clustering of granular assemblies with temperature dependent restitution and under differential rotation"
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Kurths, Jürgen
A1  - Seehafer, Norbert
A1  - Spahn, Frank
T1  - Nichtlineare Dynamik in der Physik : Forschungsbeispiele und Forschungstrends
Y1  - 1999
UR  - http://www.phil.uni-augsburg.de/dgksnd
SN  - 3-540-65329- 5
ER  - 
TY  - JOUR
A1  - Schwarz, Udo
A1  - Spahn, Frank
A1  - Grebogi, Celso
A1  - Kurths, Jürgen
A1  - Petzschmann, Olaf
T1  - Length scales of clustering in granular gases
Y1  - 1999
ER  - 
TY  - INPR
A1  - Thiessenhusen, Kai-Uwe
A1  - Esposito, Larry W.
A1  - Kurths, Jürgen
A1  - Spahn, Frank
T1  - Detection of hidden resonances in Saturn's B-ring
N2  - The Voyager 2 Photopolarimeter experiment has yielded the highest resolved data of Saturn's rings, exhibiting a wide variety of features. The B-ring region between 105000 km and 110000 km distance from Saturn has been investigated. It has a high matter density and contains no significance features visible by eye. Analysis with statistical methods has let us to the detection of two significant events. These features are correlated with the inner 3:2 resonances of the F-ring shepherd satellites Pandora and Prometheus, and may be evidence of large ring paricles caught in the corotation resonances.
T3  - NLD Preprints - 13 
KW  - Planetary Rings
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13618
ER  - 
TY  - JOUR
A1  - Spahn, Frank
A1  - Schwarz, Udo
A1  - Kurths, Jürgen
T1  - Clustering of granular assemblies with temperature dependent restitution under Keplerian differential rotation
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Spahn, Frank
A1  - Katzorke, Ines
A1  - Petzschmann, Olaf
A1  - Schwarz, Udo
A1  - Kurths, Jürgen
T1  - Cluster instabiliy of granular assemblies
Y1  - 1997
ER  -