Publications (28)
Eddy viscosity and turbulent Schmidt number by kink-type instability of strong toroidal magnetic fields
G. Ruediger, M. Gellert, M. Schultz
The potential of the nonaxisymmetric magnetic instability to transport angular momentum and to mix chemicals is probed considering the stability of a nearly uniform toroidal field…
The linear MHD Taylor-Couette instability for liquid sodium
G. Rüdiger, M. Schultz, D. Shalybkov
The linear stability of MHD Taylor-Couette flow of infinite vertical extension is considered for liquid sodium with its small magnetic Prandtl number Pm of order of 10^-5 and an un…
A non-axisymmetric magnetorotational instability of a purely toroidal magnetic field
R. Hollerbach, G. Rudiger, M. Schultz +1
We consider the flow of an electrically conducting fluid between differentially rotating cylinders, in the presence of an externally imposed toroidal field B_0 (r_i/r) e_phi. It is…
Suppression of the large-scale Lorentz force by turbulence
G. Ruediger, L. L. Kitchatinov, M. Schultz
The components of the total stress tensor (Reynolds stress plus Maxwell stress) are computed within the quasilinear approximation for a driven turbulence influenced by a large-scal…
The pinch-type instability of helical magnetic fields
G. Ruediger, M. Schultz, D. Elstner
To find out whether toroidal field can stably exist in galaxies the current-driven instability of toroidal magnetic fields is considered under the influence of an axial magnetic fi…
Dissipative Taylor-Couette flows under the influence of helical magnetic fields
G. Ruediger, M. Gellert, M. Schultz +1
The linear stability of MHD Taylor-Couette flows in axially unbounded cylinders is considered, for magnetic Prandtl number unity. Magnetic fields varying from purely axial to purel…
Nonaxisymmetric patterns in the linear theory of MHD Taylor-Couette instability
D. A. Shalybkov, G. Rüdiger, M. Schultz
The linear stability of MHD Taylor-Couette flow of infinite vertical extension is considered for various magnetic Prandtl numbers Pm. The calculations are performed for a wide gap…
The stratorotational instability of Taylor-Couette flows of moderate Reynolds numbers
G. Rüdiger, T. Seelig, M. Schultz +3
In view of new experimental data the instability against adiabatic nonaxisymmetric perturbations of a Taylor-Couette flow with an axial density stratification is considered in depe…
A 490 GHz planar circuit balanced Nb-AlO-Nb quasiparticle mixer for radio astronomy: Application to quantitative local oscillator noise determination
M. P. Westig, M. Justen, K. Jacobs +4
This article presents a heterodyne experiment which uses a 380-520 GHz planar circuit balanced Nb--Nb superconductor-insulator-superconductor (SIS) quasiparticle…
Nonaxisymmetric MHD instabilities of Chandrasekhar states in Taylor-Couette geometry
M. Gellert, G. Rüdiger, M. Schultz +2
We consider axially periodic Taylor-Couette geometry with insulating boundary conditions. The imposed basic states are so-called Chandrasekhar states, where the azimuthal flow $U_Ï…
The gap-size influence on the excitation of magnetorotational instability in cylindrical Couette flows
G. Rüdiger, M. Schultz
The excitation conditions of the magnetorotational instability are studied for axially unbounded Taylor-Couette flows of various gap widths between the cylinders. The cylinders are…
Non-diffusive angular momentum transport in rotating -pinches
G. Rüdiger, M. Schultz
The stability of conducting Taylor-Couette flows under the presence of toroidal magnetic background fields is considered. For strong enough magnetic amplitudes such magnetohydrodyn…
The Tayler instability of toroidal magnetic fields in a columnar gallium experiment
G. Ruediger, M. Schultz, M. Gellert
The nonaxisymmetric Tayler instability of toroidal magnetic fields due to axial electric currents is studied for conducting incompressible fluids between two coaxial cylinders with…
Destabilisation of hydrodynamically stable rotation laws by azimuthal magnetic fields
G. Ruediger, R. Hollerbach, M. Schultz +1
We consider the effect of toroidal magnetic fields on hydrodynamically stable Taylor-Couette differential rotation flows. For current-free magnetic fields a nonaxisymmetric m=1 mag…
The effective magnetic Prandtl number in magnetized and differentially rotating stellar radiation zones
G. Ruediger, M. Schultz, L. L. Kitchatinov
With application to inner stellar radiative zones, a linear theory is used to analyze the instability of a dipole-parity toroidal background field, in the presence of density strat…
Balanced superconductor-insulator-superconductor mixer on a 9~m silicon membrane
M. P. Westig, K. Jacobs, J. Stutzki +3
We present a 380-520 GHz balanced superconductor-insulator-superconductor (SIS) mixer on a single silicon substrate. All radio-frequency (RF) circuit components are fabricated on a…
The stability of MHD Taylor-Couette flow with current-free spiral magnetic fields between conducting cylinders
G. Ruediger, R. Hollerbach, M. Schultz +1
We study the magnetorotational instability in cylindrical Taylor-Couette flow, with the (vertically unbounded) cylinders taken to be perfect conductors, and with externally imposed…
On the toroidal-velocity anti-dynamo theorem under the presence of nonuniform electric conductivity
G. Rüdiger, M. Schultz
Laminar electrically conducting Couette flows with the hydrodynamically stable quasi-Keplerian rotation profile and non-uniform conductivity are probed for dynamo instability. In s…
Terahertz hot electron bolometer waveguide mixers for GREAT
P. Pütz, C. E. Honingh, K. Jacobs +3
Supplementing the publications based on the first-light observations with the German Receiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background informa…
Tayler instability of toroidal magnetic fields in MHD Taylor-Couette flows
G. Ruediger, M. Schultz
The nonaxisymmetric 'kink-type' Tayler instability (TI) of toroidal magnetic fields is studied for conducting incompressible fluids of uniform density between two infinitely long c…
Large-scale dynamo action of magnetized Taylor-Couette flows
G. Rüdiger, M. Schultz
A conducting Taylor-Couette flow with quasi-Keplerian rotation law containing a toroidal magnetic field serves as a mean-field dynamo model of the Tayler-Spruit-type. The flows are…
Theory of current instability experiments in magnetic Taylor-Couette flows
G. Ruediger, M. Schultz, D. Shalybkov +1
We consider the linear stability of dissipative MHD Taylor-Couette flow with imposed toroidal magnetic fields. The inner and outer cylinders can be either insulating or conducting;…
Subcritical excitation of the current-driven Tayler instability by super-rotation
G. Rüdiger, M. Schultz, M. Gellert +1
It is known that in a hydrodynamic Taylor-Couette system uniform rotation or a rotation law with positive shear ('super-rotation') are linearly stable. It is also known that a cond…
Astrophysical and experimental implications from the magnetorotational instability of toroidal fields
G. Ruediger, M. Gellert, M. Schultz +2
The interaction of differential rotation and toroidal fields that are current-free in the gap between two corotating axially unbounded cylinders is considered. It is shown that non…
The angular momentum transport by standard MRI in quasi-Kepler cylindric Taylor-Couette flows
M. Gellert, G. Rüdiger, M. Schultz
The instability of a quasi-Kepler flow in dissipative Taylor-Couette systems under the presence of an homogeneous axial magnetic field is considered with focus to the excitation of…
HIFI spectroscopy of low-level water transitions in M82
A. Weiss, M. A. Requena-Torres, R. Guesten +23
We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal s…
Destabilization of super-rotating Taylor-Couette flows by current-free helical magnetic fields
G. Rüdiger, M. Schultz, R. Hollerbach
In an earlier paper we showed that the combination of azimuthal magnetic fields and super-rotation in Taylor-Couette flows of conducting fluids can be unstable against non-axisymme…
Field-dependent anisotropic magnetoresistance and planar Hall effect in epitaxial magnetite thin films
N. Naftalis, A. Kaplan, M. Schultz +4
A systematic study of the temperature and magnetic field dependence of the longitudinal and transverse resistivities of epitaxial thin films of magnetite (Fe3O4) is reported. The a…