@article{PetzschmannThiessenhusenSpahnetal.1998, author = {Petzschmann, Olaf and Thiessenhusen, Kai-Uwe and Spahn, Frank and Schmidt, J{\"u}rgen}, title = {Inelastic collisions in planetary rings : thickness and satellite-induced structures}, isbn = {0-7923-5102-9}, year = {1998}, language = {en} } @article{SaloPetzschmannSpahnetal.1999, author = {Salo, H. and Petzschmann, Olaf and Spahn, Frank and Schmidt, J{\"u}rgen}, title = {Vertical distribution of temperature and density in a planetary ring}, year = {1999}, language = {en} } @phdthesis{Schmidt2000, author = {Schmidt, J{\"u}rgen}, title = {Oscillatory instability of dense and dissipative keplerian shear flow}, pages = {99 S.}, year = {2000}, language = {en} } @article{SpahnSchmidtPetzschmannetal.2000, author = {Spahn, Frank and Schmidt, J{\"u}rgen and Petzschmann, Olaf and Salo, H.}, title = {Stability analysis of a Keplarian disk of granular grains : influence of thermal diffusion}, year = {2000}, language = {en} } @article{SpahnSchmidtSremcevic2000, author = {Spahn, Frank and Schmidt, J{\"u}rgen and Sremcevic, Miodrag}, title = {Structures in planetary rings : stability and gravitational scattering}, isbn = {3-540-41074-0}, year = {2000}, language = {en} } @article{SaloSchmidtSpahn2001, author = {Salo, H. and Schmidt, J{\"u}rgen and Spahn, Frank}, title = {Viscous overstability in Saturn's B ring : I. Direct simulations and measurements of transport coefficients}, year = {2001}, language = {en} } @article{SchmidtSaloSpahn2001, author = {Schmidt, J{\"u}rgen and Salo, H. and Spahn, Frank}, title = {Viscous overstability in Saturn's B ring : II. Hydrodynamic theory and comparison to simulations}, year = {2001}, language = {en} } @article{SpahnPetzschmannSchmidtetal.2001, author = {Spahn, Frank and Petzschmann, Olaf and Schmidt, J{\"u}rgen and Sremcevic, Miodrag and Hertzsch, Jan-Martin}, title = {About the viscosity of granular gases : the force-free case versus granular gases under Keplarian differential rotation}, isbn = {3-540-41458-4}, year = {2001}, language = {en} } @article{GordonKrivovSchmidtetal.2002, author = {Gordon, M. K. and Krivov, Alexander V. and Schmidt, J{\"u}rgen and Spahn, Frank}, title = {Planetary rings}, year = {2002}, language = {en} } @article{SpahnSchmidtAlbersetal.2006, author = {Spahn, Frank and Schmidt, J{\"u}rgen and Albers, Nicole and H{\"o}rning, Marcel and Makuch, Martin and Seiß, Martin and Kempf, Sascha and Srama, Ralf and Dikarev, Valeri and Helfert, Stefan and Moragas-Klostermeyer, Georg and Krivov, Alexander V. and Sremcevic, Miodrag and Tuzzolino, Anthony J. and Economou, Thanasis and Gr{\"u}n, Eberhard}, title = {Cassini dust measurements at Enceladus and implications for the origin of the E ring}, doi = {10.1126/science.1121375}, year = {2006}, language = {en} } @article{SpahnSchmidt2006, author = {Spahn, Frank and Schmidt, J{\"u}rgen}, title = {Planetary science : Saturn's bared mini-moons}, doi = {10.1038/440614a}, year = {2006}, language = {en} } @article{MontbrioPazoSchmidt2006, author = {Montbrio, Ernest and Pazo, Diego and Schmidt, J{\"u}rgen}, title = {Time delay in the Kuramoto model with bimodal frequency distribution}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {74}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, publisher = {APS}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.74.056201}, pages = {5}, year = {2006}, abstract = {We investigate the effects of a time-delayed all-to-all coupling scheme in a large population of oscillators with natural frequencies following a bimodal distribution. The regions of parameter space corresponding to synchronized and incoherent solutions are obtained both numerically and analytically for particular frequency distributions. In particular, we find that bimodality introduces a new time scale that results in a quasiperiodic disposition of the regions of incoherence.}, language = {en} } @book{BeckerBenedensDeppeetal.2006, author = {Becker, Ulrich and Benedens, Niels Peter and Deppe, Volker and D{\"u}wel, Martin and Hermann, Klaus and Kluge, Johannes and Liedtke, Frank and Schmidt, J{\"u}rgen and Schmidt, Thorsten Ingo and Baum, Christoph}, title = {Kommunalabgabengesetz f{\"u}r das Land Brandenburg}, series = {Gesetze, Verordnungen, Kommentare}, journal = {Gesetze, Verordnungen, Kommentare}, publisher = {Kommunal- und Schul-Verlag}, address = {Wiesbaden}, isbn = {978-3-8293-0764-2}, year = {2006}, abstract = {Das Kommunalabgabengesetz f{\"u}r das Land Brandenburg (KAG) ist eine f{\"u}r alle Kommunalverwaltungen, Zweckverb{\"a}nde und Anw{\"a}lte wichtige Rechtsmaterie. Den 20 Paragrafen steht eine F{\"u}lle von Fragen nach Auslegung und Anwendung des Gesetzes gegen{\"u}ber, die von der Rechtsprechung mit zahlreichen Entscheidungen beantwortet werden. Mit dem Werk "Kommunalabgabengesetz f{\"u}r das Land Brandenburg" liegt ein umfassender Kommentar vor, der sich mit der Auslegung des brandenburgischen Kommunalabgabengesetzes (KAG) und der dazu ergangenen Rechtsprechung befasst. Die zahlreichsten Gerichtsentscheidungen beinhaltet die Kommentierung zu \S 6 (Benutzungsgeb{\"u}hren) Einerseits darf der Titel f{\"u}r sich in Anspruch nehmen, auch nicht speziell juristisch ausgebildete Nutzer in die Rechtsvorschriften zum KAG Brandenburg einzuf{\"u}hren. Andererseits will es aber auch den mit dem Abgabenrecht befassten Fachleuten in Verwaltungen, Verb{\"a}nden, Gerichten und Kanzleien eine solide Grundlage f{\"u}r m{\"o}glichst rechtssichere Entscheidungen bieten. Der engen r{\"a}umlichen N{\"a}he wegen beinhaltet das Werk die Abgabenrechtlichen Vorschriften des Landes Berlin.}, language = {de} } @article{BrilliantovSchmidt2009, author = {Brilliantov, Nikolai V. and Schmidt, J{\"u}rgen}, title = {Aggregation kinetics in a flow : the role of particle-wall collisions}, issn = {1951-6355}, doi = {10.1140/epjst/e2009-01006-X}, year = {2009}, abstract = {Agglomeration in a fluid flow, when collisions of aggregates with channel walls are important is analyzed. We assume the diffusion-limited mechanism for clusters growth and the Stokes' force exerted on the agglomerates from the flow. Collisions of the particles with the channel walls are modeled by a random Poisson process. We develop an analytical theory for the size distribution of the aggregates and check the theoretical predictions by Monte Carlo simulations. The numerical data agree well with the analytical results.}, language = {en} } @article{JonesArridgeCoatesetal.2009, author = {Jones, Geraint H. and Arridge, Christopher S. and Coates, Andrew J. and Lewis, Gethyn R. and Kanani, Sheila and Wellbrock, Anne and Young, David T. and Crary, Frank J. and Tokar, Robert L. and Wilson, R. J. and Hill, Thomas W. and Johnson, Robert E. and Mitchell, Donald G. and Schmidt, J{\"u}rgen and Kempf, Sascha and Beckmann, Uwe and Russell, Christopher T. and Jia, Y. D. and Dougherty, Michele K. and Waite, J. Hunter and Magee, Brian A.}, title = {Fine jet structure of electrically charged grains in Enceladus' plume}, issn = {0094-8276}, doi = {10.1029/2009gl038284}, year = {2009}, abstract = {By traversing the plume erupting from high southern latitudes on Saturn's moon Enceladus, Cassini orbiter instruments can directly sample the material therein. Cassini Plasma Spectrometer, CAPS, data show that a major plume component comprises previously-undetected particles of nanometer scales and larger that bridge the mass gap between previously observed gaseous species and solid icy grains. This population is electrically charged both negative and positive, indicating that subsurface triboelectric charging, i.e., contact electrification of condensed plume material may occur through mutual collisions within vents. The electric field of Saturn's magnetosphere controls the jets' morphologies, separating particles according to mass and charge. Fine-scale structuring of these particles' spatial distribution correlates with discrete plume jets' sources, and reveals locations of other possible active regions. The observed plume population likely forms a major component of high velocity nanometer particle streams detected outside Saturn's magnetosphere.}, language = {en} } @article{PostbergKempfSchmidtetal.2009, author = {Postberg, Frank and Kempf, Sascha and Schmidt, J{\"u}rgen and Brilliantov, Nikolai V. and Beinsen, Alexander and Abel, Bernd and Buck, Udo and Srama, Ralf}, title = {Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus}, issn = {0028-0836}, doi = {10.1038/Nature08046}, year = {2009}, abstract = {Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole(1-5), suggesting the possibility of a subsurface ocean(5-7). These plume particles are the dominant source of Saturn's E ring(7,8). A previous in situ analysis(9) of these particles concluded that the minor organic or siliceous components, identified in many ice grains, could be evidence for interaction between Enceladus' rocky core and liquid water(9,10). It was not clear, however, whether the liquid is still present today or whether it has frozen. Here we report the identification of a population of E-ring grains that are rich in sodium salts (similar to 0.5- 2\% by mass), which can arise only if the plumes originate from liquid water. The abundance of various salt components in these particles, as well as the inferred basic pH, exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core(11). The plume vapour is expected to be free of atomic sodium. Thus, the absence of sodium from optical spectra(12) is in good agreement with our results. In the E ring the upper limit for spectroscopy(12) is insufficiently sensitive to detect the concentrations we found.}, language = {en} } @article{ShepelyanskyPikovskijSchmidtetal.2009, author = {Shepelyansky, Dima L. and Pikovskij, Arkadij and Schmidt, J{\"u}rgen and Spahn, Frank}, title = {Synchronization mechanism of sharp edges in rings of Saturn}, issn = {0035-8711}, doi = {10.1111/j.1365-2966.2009.14719.x}, year = {2009}, abstract = {We propose a new mechanism which explains the existence of enormously sharp edges in the rings of Saturn. This mechanism is based on the synchronization phenomenon due to which the epicycle rotational phases of particles in the ring, under certain conditions, become synchronized with the phase of external satellite, e. g. with the phase of Mimas in the case of the outer B ring edge. This synchronization eliminates collisions between particles and suppresses the diffusion induced by collisions by orders of magnitude. The minimum of the diffusion is reached at the centre of the synchronization regime corresponding to the ratio 2:1 between the orbital frequency at the edge of B ring and the orbital frequency of Mimas. The synchronization theory gives the sharpness of the edge in a few tens of meters that is in agreement with available observations.}, language = {en} } @article{SeissSpahnSchmidt2010, author = {Seiß, Martin and Spahn, Frank and Schmidt, J{\"u}rgen}, title = {Moonlet induced wakes in planetary rings : analytical model including eccentric orbits of moon and ring particles}, issn = {0019-1035}, doi = {10.1016/j.icarus.2010.06.013}, year = {2010}, abstract = {Saturn's rings host two known moons, Pan and Daphnis, which are massive enough to clear circumferential gaps in the ring around their orbits. Both moons create wake patterns at the gap edges by gravitational deflection of the ring material (Cuzzi, J.N., Scargle, J.D. [1985]. Astrophys. J. 292, 276-290; Showalter, MR., Cuzzi, J.N., Marouf, E.A., Esposito, LW. [1986]. Icarus 66, 297-323). New Cassini observations revealed that these wavy edges deviate from the sinusoidal waveform, which one would expect from a theory that assumes a circular orbit of the perturbing moon and neglects particle interactions. Resonant perturbations of the edges by moons outside the ring system, as well as an eccentric orbit of the embedded moon, may partly explain this behavior (Porco, CC., and 34 colleagues [2005]. Science 307, 1226-1236; Tiscareno, M.S., Burns, J.A., Hedman, MM., Spitale, J.N., Porco, CC., Murray, C.D., and the Cassini Imaging team [2005]. Bull. Am. Astron. Soc. 37, 767; Weiss, J.W., Porco, CC., Tiscareno, M.S., Burns, J.A., Dones, L [2005]. Bull. Am. Astron. Soc. 37, 767; Weiss, J.W., Porco, CC., Tiscareno, M.S. [2009]. Astron. J. 138, 272-286). Here we present an extended non-collisional streamline model which accounts for both effects. We describe the resulting variations of the density structure and the modification of the nonlinearity parameter q. Furthermore, an estimate is given for the applicability of the model. We use the streamwire model introduced by Stewart (Stewart, G.R. [1991]. Icarus 94, 436-450) to plot the perturbed ring density at the gap edges. We apply our model to the Keeler gap edges undulated by Daphnis and to a faint ringlet in the Encke gap close to the orbit of Pan. The modulations of the latter ringlet, induced by the perturbations of Pan (Burns, J.A., Hedman, M.M., Tiscareno, M.S., Nicholson, P.D., Streetman, B.J., Colwell, J.E., Showalter, M.R., Murray, C.D., Cuzzi, J.N., Porco, CC., and the Cassini ISS team [2005]. Bull. Am. Astron. Soc. 37, 766), can be well described by our analytical model. Our analysis yields a Hill radius of Pan of 17.5 km, which is 9\% smaller than the value presented by Porco (Porco, CC., and 34 colleagues [2005]. Science 307, 1226- 1236), but fits well to the radial semi-axis of Pan of 17.4 km. This supports the idea that Pan has filled its Hill sphere with accreted material (Porco, C.C., Thomas, P.C., Weiss, J.W., Richardson, D.C. [2007]. Science 318, 1602-1607). A numerical solution of a streamline is used to estimate the parameters of the Daphnis-Keeler gap system, since the close proximity of the gap edge to the moon induces strong perturbations, not allowing an application of the analytic streamline model. We obtain a Hill radius of 5.1 km for Daphnis, an inner edge variation of 8 km, and an eccentricity for Daphnis of 1.5 x 10(-5). The latter two quantities deviate by a factor of two from values gained by direct observations (Jacobson, R.A., Spitale, J., Porco, C.C., Beurle, K., Cooper, N.J., Evans, M.W., Murray, C.D. [2008]. Astron. J. 135, 261-263; Tiscareno, M.S., Burns, J.A., Hedman, M.M., Spitale, J.N., Porco, C.C., Murray, C.D., and the Cassini Imaging team [2005]. Bull. Am. Astron. Soc. 37, 767), which might be attributed to the neglect of particle interactions and vertical motion in our model.}, language = {en} } @article{TobieGieseHurfordetal.2010, author = {Tobie, Gabriel and Giese, Bernd and Hurford, Terry Anthony and Lopes, Rosaly M. and Nimmo, Francis and Postberg, Frank and Retherford, Kurt D. and Schmidt, J{\"u}rgen and Spencer, John R. and Tokano, Tetsuya and Turtle, Elizabeth P.}, title = {Surface, subsurface and atmosphere exchanges on the satellites of the outer solar system}, issn = {0038-6308}, doi = {10.1007/s11214-010-9641-3}, year = {2010}, abstract = {The surface morphology of icy moons is affected by several processes implicating exchanges between their subsurfaces and atmospheres (if any). The possible exchange of material between the subsurface and the surface is mainly determined by the mechanical properties of the lithosphere, which isolates the deep, warm and ductile ice material from the cold surface conditions. Exchanges through this layer occur only if it is sufficiently thin and/or if it is fractured owing to tectonic stresses, melt intrusion or impact cratering. If such conditions are met, cryomagma can be released, erupting fresh volatile-rich materials onto the surface. For a very few icy moons (Titan, Triton, Enceladus), the emission of gas associated with cryovolcanic activity is sufficiently large to generate an atmosphere, either long- lived or transient. For those moons, atmosphere-driven processes such as cryovolcanic plume deposition, phase transitions of condensable materials and wind interactions continuously re-shape their surfaces, and are able to transport cryovolcanically generated materials on a global scale. In this chapter, we discuss the physics of these different exchange processes and how they affect the evolution of the satellites' surfaces.}, language = {en} } @article{CuzziBurnsCharnozetal.2010, author = {Cuzzi, Jeff N. and Burns, Joseph A. and Charnoz, S{\´e}bastien and Clark, Roger N. and Colwell, Josh E. and Dones, Luke and Esposito, Larry W. and Filacchione, Gianrico and French, Richard G. and Hedman, Matthew M. and Kempf, Sascha and Marouf, Essam A. and Murray, Carl D. and Nicholson, Phillip D. and Porco, Carolyn C. and Schmidt, J{\"u}rgen and Showalter, Mark R. and Spilker, Linda J. and Spitale, Joseph N. and Srama, Ralf and Sremcević, Miodrag and Tiscareno, Matthew Steven and Weiss, John}, title = {An evolving view of Saturn's dynamic rings}, issn = {0036-8075}, doi = {10.1126/science.1179118}, year = {2010}, abstract = {We review our understanding of Saturn's rings after nearly 6 years of observations by the Cassini spacecraft. Saturn's rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-gravity of innumerable orbiting centimeter- to meter-sized particles, and the effects of several peripheral and embedded moonlets, but much remains unexplained. A few aspects of ring structure change on time scales as short as days. It remains unclear whether the vigorous evolutionary processes to which the rings are subject imply a much younger age than that of the solar system. Processes on view at Saturn have parallels in circumstellar disks.}, language = {en} }