Low-frequency zonal flow eigen-structure in tokamak plasmas

2021 ◽  
Author(s):  
V I Ilgisonis ◽  
Vladimir P Lakhin ◽  
Nikita Marusov ◽  
Andrei I Smolyakov ◽  
Ekaterina Sorokina
Keyword(s):  
Low Frequency ◽  
Zonal Flow ◽  
Tokamak Plasma ◽  
Tokamak Plasmas ◽  
Plasma Parameters ◽  
Plasma Rotation ◽  
Zonal Flows ◽  
Toroidal Plasma ◽  
Flow Formation ◽  
Eigenmode Analysis

Abstract The nonlocal eigenmode analysis of low-frequency zonal flows in toroidally rotating tokamak plasmas is performed in the framework of the reduced one-fluid ideal MHD-model. It is shown that for typical profiles of plasma parameters toroidal plasma rotation results in the global zonal flow formation on the periphery of plasma column. For some types of equilibria these zonal flows are aperiodically unstable that leads to the excitation of the differential plasma rotation at the tokamak plasma edge.

scholarly journals Experimental and numerical studies of an eastward jet over topography

2001 ◽  
Vol 438 ◽  
pp. 129-157 ◽  
Author(s):  
YUDONG TIAN ◽  
ERIC R. WEEKS ◽  
KAYO IDE ◽  
J. S. URBACH ◽  
CHARLES N. BAROUD ◽  
...  
Keyword(s):  
Parameter Space ◽  
Laboratory Experiments ◽  
Multiple Equilibria ◽  
Low Frequency ◽  
Zonal Flow ◽  
Azimuthal Velocity ◽  
Flow Patterns ◽  
Initial State ◽  
Similar Frequency ◽  
Zonal Flows

Motivated by the phenomena of blocked and zonal flows in Earth's atmosphere, we conducted laboratory experiments and numerical simulations to study the dynamics of an eastward jet flowing over wavenumber-two topography. The laboratory experiments studied the dynamical behaviour of the flow in a barotropic rotating annulus as a function of the experimental Rossby and Ekman numbers. Two distinct flow patterns, resembling blocked and zonal flows in the atmosphere, were observed to persist for long time intervals.Earlier model studies had suggested that the atmosphere's normally upstream- propagating Rossby waves can resonantly lock to the underlying topography, and that this topographic resonance separates zonal from blocked flows. In the annulus, the zonal flows did indeed have super-resonant mean zonal velocities, while the blocked flows appear subresonant. Low-frequency variability, periodic or irregular, was present in the measured time series of azimuthal velocity in the blocked regime, with dominant periodicities in the range of 6–25 annulus rotations. Oscillations have also been detected in zonal states, with smaller amplitude and similar frequency. In addition, over a large region of parameter space the two flow states exhibited spontaneous, intermittent transitions from the one to the other.We numerically simulated the laboratory flow geometry in a quasi-geostrophic barotropic model over a similar range of parameters. Both flow regimes, blocked and zonal, were reproduced in the simulations, with similar spatial and temporal characteristics, including the low-frequency oscillations associated with the blocked flow. The blocked and zonal flow patterns are present over wide ranges of forcing, topographic height, and bottom friction. For a significant portion of parameter space, both model flows are stable. Depending on the initial state, either the blocked or the zonal flow is obtained and persists indefinitely, showing the existence of multiple equilibria.

Influence of non-monochromaticity on zonal-flow generation by magnetized Rossby waves in the ionospheric E-layer

2009 ◽  
Vol 75 (3) ◽  
pp. 345-357 ◽  
Author(s):  
T. D. KALADZE ◽  
H. A. SHAH ◽  
G. MURTAZA ◽  
L. V. TSAMALASHVILI ◽  
M. SHAD ◽  
...  
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Low Frequency ◽  
Zonal Flow ◽  
Present Theory ◽  
Resonant Interaction ◽  
Finite Amplitude ◽  
Small Scale ◽  
Zonal Flows ◽  
Flow Generation

AbstractThe influence of non-monochromaticity on low-frequency, large-scale zonal-flow nonlinear generation by small-scale magnetized Rossby (MR) waves in the Earth's ionospheric E-layer is considered. The modified parametric approach is used with an arbitrary spectrum of primary modes. It is shown that the broadening of the wave packet spectrum of pump MR waves leads to a resonant interaction with a growth rate of the order of the monochromatic case. In the case when zonal-flow generation by MR modes is prohibited by the Lighthill stability criterion, the so-called two-stream-like mechanism for the generation of sheared zonal flows by finite-amplitude MR waves in the ionospheric E-layer is possible. The growth rates of zonal-flow instabilities and the conditions for driving them are determined. The present theory can be used for the interpretation of the observations of Rossby-type waves in the Earth's ionosphere and in laboratory experiments.

scholarly journals Numerical and Experimental Investigation of Longitudinal Oscillations in Hall Thrusters

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 148
Author(s):  
Vittorio Giannetti ◽  
Manuel Martín Saravia ◽  
Luca Leporini ◽  
Simone Camarri ◽  
Tommaso Andreussi
Keyword(s):  
Discharge Current ◽  
Fluid Model ◽  
Low Frequency ◽  
Hall Thruster ◽  
Hall Thrusters ◽  
Current Signal ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Breathing Mode ◽  
Spatio Temporal

One of the main oscillatory modes found ubiquitously in Hall thrusters is the so-called breathing mode. This is recognized as a relatively low-frequency (10–30 kHz), longitudinal oscillation of the discharge current and plasma parameters. In this paper, we present a synergic experimental and numerical investigation of the breathing mode in a 5 kW-class Hall thruster. To this aim, we propose the use of an informed 1D fully-fluid model to provide augmented data with respect to available experimental measurements. The experimental data consists of two datasets, i.e., the discharge current signal and the local near-plume plasma properties measured at high-frequency with a fast-diving triple Langmuir probe. The model is calibrated on the discharge current signal and its accuracy is assessed by comparing predictions against the available measurements of the near-plume plasma properties. It is shown that the model can be calibrated using the discharge current signal, which is easy to measure, and that, once calibrated, it can predict with reasonable accuracy the spatio-temporal distributions of the plasma properties, which would be difficult to measure or estimate otherwise. Finally, we describe how the augmented data obtained through the combination of experiments and calibrated model can provide insight into the breathing mode oscillations and the evolution of plasma properties.

scholarly journals Toroidal plasma rotation in the PLT tokamak with neutral-beam injection

1981 ◽  
Vol 21 (10) ◽  
pp. 1301-1309 ◽  
Author(s):  
S. Suckewer ◽  
H.P. Eubank ◽  
R.J. Goldston ◽  
J. McEnerney ◽  
N.R. Sauthoff ◽  
...  
Keyword(s):  
Neutral Beam Injection ◽  
Neutral Beam ◽  
Plasma Rotation ◽  
Toroidal Plasma ◽  
Beam Injection

scholarly journals COMPARISON BETWEEN 2D TURBULENCE MODEL ESEL AND EXPERIMENTAL DATA FROM AUG AND COMPASS TOKAMAKS

2015 ◽  
Vol 55 (2) ◽  
pp. 128-135 ◽  
Author(s):  
Peter Ondac ◽  
Jan Horacek ◽  
Jakub Seidl ◽  
Petr Vondrácek ◽  
Hans Werner Müller ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Plasma Potential ◽  
Density Fluctuations ◽  
Tokamak Plasma ◽  
Plasma Parameters ◽  
Fluid Turbulence ◽  
Radial Profiles ◽  
Parallel Dynamics ◽  
Two Machines ◽  
Probe Measurements

<!-- p, li { white-space: pre-wrap; } --><p style="text-indent: 0px; margin: 0px;">In this article we have used the 2D fluid turbulence numerical model, ESEL, to simulate turbulent transport in edge tokamak plasma. Basic plasma parameters from the ASDEX Upgrade and COMPASS tokamaks are used as input for the model, and the output is compared with experimental observations obtained by reciprocating probe measurements from the two machines. Agreements were found in radial profiles of mean plasma potential and temperature, and in a level of density fluctuations. Disagreements, however, were found in the level of plasma potential and temperature fluctuations. This implicates a need for an extension of the ESEL model from 2D to 3D to fully resolve the parallel dynamics, and the coupling from the plasma to the sheath.</p>

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