iff-Überschuldungsreport 2011: Überschuldung in Deutschland

Studie über die Situation von privater Überschuldung betroffener Menschen in Deutschland in den Jahren 2006 bis 2010: Ausgewertet wurden die Daten von insgesamt 13.052 überschuldeten Haushalten in 9 Schuldner­beratungsstellen. Die Studie zeigt die Auswirkungen der Wirtschaftskrise, stellt den Zusammenhang zwischen Bildung, Arbeitslosigkeit und Überschuldung dar und enthält detaillierte Auswertungen zu den einzelnen Gläubiger- und Schuldnergruppen sowie Handlungsempfehlungen. --

iff-Überschuldungsreport 2009: Überschuldung in Deutschland

Studie über die Situation von privater Überschuldung betroffener Menschen in Deutschland in den Jahren 2004 bis 2008: Ausgewertet wurden die Daten von insgesamt 11.773 überschul­deten Haushalten in 9 Schuldnerberatungsstellen. Die Studie stellt erstmals die Dauer des Überschuldungsprozesses dar und zeigt typische Verläufe bei Überschuldeten. --

iff-Überschuldungsreport 2008: Private Überschuldung in Deutschland

Studie über die Situation von privater Überschuldung betroffener Menschen in Deutschland in den Jahren 2003 bis 2007: Ausgewertet wurden die Daten von insgesamt 9.159 überschul­deten Haushalten in 9 Schuldnerberatungsstellen. Die Studie stellt erstmals den Zusammenhang zwischen Armut und Überschuldung detailliert empirisch dar; betrachtet die zeitlichen Abläufe im Prozess der Überschuldung und verfügt über einen ausgiebigen Tabellenanhang mit Vergleichen zwischen überschuldeten Haushalten und der Bevölkerung insgesamt. --

A nonlinear model for rotationally constrained convection with Ekman pumping

It is a well established result of linear theory that the influence of differing mechanical boundary conditions, i.e., stress-free or no-slip, on the primary instability in rotating convection becomes asymptotically small in the limit of rapid rotation. This is accounted for by the diminishing impact of the viscous stresses exerted within Ekman boundary layers and the associated vertical momentum transport by Ekman pumping. By contrast, in the nonlinear regime recent experiments and supporting simulations are now providing evidence that the efficiency of heat transport remains strongly influenced by Ekman pumping in the rapidly rotating limit. In this paper, a reduced model is developed for the case of low Rossby number convection in a plane layer geometry with no-slip upper and lower boundaries held at fixed temperatures. A complete description of the dynamics requires the existence of three distinct regions within the fluid layer: a geostrophically balanced interior where fluid motions are predominately aligned with the axis of rotation, Ekman boundary layers immediately adjacent to the bounding plates, and thermal wind layers driven by Ekman pumping in between. The reduced model uses a classical Ekman pumping parameterization to alleviate the need for spatially resolving the Ekman boundary layers. Results are presented for both linear stability theory and a special class of nonlinear solutions described by a single horizontal spatial wavenumber. It is shown that Ekman pumping allows for significant enhancement in the heat transport relative to that observed in simulations with stress-free boundaries. Without the intermediate thermal wind layer the nonlinear feedback from Ekman pumping would be able to generate a heat transport that diverges to infinity. This layer arrests this blowup resulting in finite heat transport at a significantly enhanced value.Comment: 38 pages, 14 figure

The Tayler instability of toroidal magnetic fields in a columnar gallium experiment

The nonaxisymmetric Tayler instability of toroidal magnetic fields due to axial electric currents is studied for conducting incompressible fluids between two coaxial cylinders without endplates. The inner cylinder is considered as so thin that even the limit of R_in \to 0 can be computed. The magnetic Prandtl number is varied over many orders of magnitudes but the azimuthal mode number of the perturbations is fixed to m=1. In the linear approximation the critical magnetic field amplitudes and the growth rates of the instability are determined for both resting and rotating cylinders. Without rotation the critical Hartmann numbers do {\em not} depend on the magnetic Prandtl number but this is not true for the growth rates. For given product of viscosity and magnetic diffusivity the growth rates for small and large magnetic Prandtl number are much smaller than those for Pm=1. For gallium under the influence of a magnetic field at the outer cylinder of 1 kG the resulting growth time is 5 s. The minimum electric current through a container of 10 cm diameter to excite the kink-type instability is 3.20 kA. For a rotating container both the critical magnetic field and the related growth times are larger than for the resting column.Comment: 7 pages, 9 figures, submitted to Astron. Nach

iff-Überschuldungsreport 2007: Private Überschuldung in Deutschland

Studie über die Situation von privater Überschuldung betroffener Menschen in Deutschland in den Jahren 2005 und 2006: Ausgewertet wurden die Daten von insgesamt 2.716 überschuldeten Haushalten. --

Tayler instability of toroidal magnetic fields in MHD Taylor-Couette flows

The nonaxisymmetric 'kink-type' Tayler instability (TI) of toroidal magnetic fields is studied for conducting incompressible fluids of uniform density between two infinitely long cylinders rotating around the same axis. It is shown that for resting cylinders the critical Hartmann number for the unstable modes does not depend on Pm. By rigid rotation the instability is suppressed where the critical ratio of the rotation velocity and the Alfven velocity of the field (only) slightly depends on the magnetic Prandtl number Pm. For Pm=1 the rotational quenching of TI takes its maximum. Rotation laws with negative shear (i.e. d\Omega/dR<0) strongly destabilize the toroidal field if the rotation is not too fast. For sufficiently high Reynolds numbers of rotation the suppression of the nonaxisymmetric magnetic instability always dominates. The angular momentum transport of the instability is anticorrelated with the shear so that an eddy viscosity can be defined which proves to be positive. For negative shear the Maxwell stress of the perturbations remarkably contributes to the angular momentum transport. We have also shown the possibility of laboratory TI experiments with a wide-gap container filled with fluid metals like sodium or gallium. Even the effect of the rotational stabilization can be reproduced in the laboratory with electric currents of only a few kAmp.Comment: 9 pages, 11 figures, sub