On resistive magnetohydrodynamic studies of sawtooth oscillations in tokamaks

2015 ◽  
Vol 22 (3) ◽  
pp. 032304 ◽  
Author(s):  
A. Y. Aydemir ◽  
J. Y. Kim ◽  
B. H. Park ◽  
J. Seol
Keyword(s):  
Sawtooth Oscillations

scholarly journals Modification of Sawtooth Oscillations with ICRF Waves in the JET Tokamak

2007 ◽  
Author(s):  
M. J. Mantsinen ◽  
B. Alper ◽  
C. Angioni ◽  
R. Buttery ◽  
S. Coda ◽  
...  
Keyword(s):  
Sawtooth Oscillations

Testing a model for triggering sawtooth oscillations in tokamaks

2006 ◽  
Vol 13 (7) ◽  
pp. 072505 ◽  
Author(s):  
Glenn Bateman ◽  
Canh N. Nguyen ◽  
Arnold H. Kritz ◽  
Franco Porcelli
Keyword(s):  
Sawtooth Oscillations

Sawtooth oscillations in a damped/driven cryogenic electron plasma: Experiment and theory

1997 ◽  
Vol 4 (6) ◽  
pp. 2062-2071 ◽  
Author(s):  
B. P. Cluggish ◽  
C. F. Driscoll ◽  
K. Avinash ◽  
J. A. Helffrich
Keyword(s):  
Electron Plasma ◽  
Plasma Experiment ◽  
Sawtooth Oscillations

Study of sawtooth oscillations on the HT-7 tokamak using 2D tomography of soft x-ray signal

2005 ◽  
Vol 14 (10) ◽  
pp. 2061-2067 ◽  
Author(s):  
Ma Tian-Peng ◽  
Hu Li-Qun ◽  
Wan Bao-Nian ◽  
Ruan Huai-Lin ◽  
Gao Xiang ◽  
...  
Keyword(s):  
X Ray ◽  
Sawtooth Oscillations

The role of stochasticity in sawtooth oscillations

1992 ◽  
Vol 32 (3) ◽  
pp. 495-512 ◽  
Author(s):  
A.J Lichtenberg ◽  
K Itoh ◽  
S.-I Itoh ◽  
A Fukuyama
Keyword(s):  
Sawtooth Oscillations

Sawtooth oscillations in shaped plasmas

2007 ◽  
Vol 14 (5) ◽  
pp. 055701 ◽  
Author(s):  
E. A. Lazarus ◽  
T. C. Luce ◽  
M. E. Austin ◽  
D. P. Brennan ◽  
K. H. Burrell ◽  
...  
Keyword(s):  
Sawtooth Oscillations

The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations

2021 ◽  
Author(s):  
Niloufar Nowrouzi ◽  
Lynn Kistler ◽  
Eric Lund ◽  
Kai Zhao
Keyword(s):  
Plasma Sheet ◽  
Statistical Study ◽  
Onset Time ◽  
Direct Access ◽  
Data Set ◽  
Superposed Epoch Analysis ◽  
3D Data ◽  
Before And After ◽  
Epoch Analysis ◽  
Sawtooth Oscillations

<p>Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during  magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O<sup>+</sup> may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O<sup>+</sup> ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O<sup>+</sup> in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.</p><p>We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e<sup>-1</sup> to 12 keV e<sup>-1</sup>.  We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on TEAMS data and produced a data set for four data species (H<sup>+</sup>, O<sup>+</sup>, and He<sup>+</sup>). From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:</p><ul><li>the averaged O<sup>+</sup> outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.</li> <li><span>Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.</span></li> <li><span>In both CME-driven and SIR-driven, the averaged O</span><sup>+</sup><span> outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.</span></li> </ul><p>We will develop this study by performing a similar statistical study for H<sup>+</sup> outflow and finally will compare the H<sup>+</sup> result with the O<sup>+ </sup>result.</p>

scholarly journals Kinetic infernal modes for Wendelstein 7-X-like -profiles

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Alessandro Zocco ◽  
Alexey Mishchenko ◽  
Axel Könies
Keyword(s):  
Electron Temperature ◽  
High Performance ◽  
Ion Temperature ◽  
Electron Temperature Gradient ◽  
Average Value ◽  
Toroidal Plasma ◽  
Rotational Transform ◽  
Ideal Magnetohydrodynamic ◽  
The One ◽  
Sawtooth Oscillations

We show analytically that for $\unicode[STIX]{x1D704}$ -profiles similar to the one of the Wendelstein 7-X stellarator, where $\unicode[STIX]{x1D704}$ is the rotational transform of the equilibrium magnetic field, a highly conducting toroidal plasma is unstable to kinetically mediated pressure-driven long-wavelength reconnecting modes, of the infernal type. The modes are destabilized either by the electron temperature gradient or by a small amount of current, depending on how far from unity the average value of $\unicode[STIX]{x1D704}$ is, which is assumed to be slowly varying. We argue that, for W7-X, a broad mode with toroidal and poloidal mode numbers $(n,m)=(1,1)$ can be destabilized due to the strong geometric side-band coupling of the resonant kinetic electron response at locations where $\unicode[STIX]{x1D704}$ is rational for harmonics that belong to the mode family of the $(n,m)=(1,1)$ mode itself. In many regimes, the growth rate is insensitive to the plasma density, thus it is likely to persist in high performance W7-X discharges. For a peaked electron temperature, with a maximum of $T_{e}=5~\text{keV}$ , larger than the ion temperature, $T_{i}=2.5~\text{keV}$ , and a density $n_{0}=10^{19}~\text{m}^{-3}$ , instability is found in regimes which show plasma sawtooth activity, with growth rates of the order of tens of kiloHertz. Frequencies are either electron diamagnetic or of the ideal magnetohydrodynamic type, but sub-Alfvénic. The kinetic infernal mode is thus a good candidate for the explanation of sawtooth oscillations in present-day stellarators and poses a new challenge to the problem of stellarator reactor optimization.

Note on a paper by Omta et al. on sawtooth oscillations

SeMA Journal ◽  
2013 ◽  
Vol 62 (1) ◽  
pp. 1-13 ◽  
Author(s):  
A. C. Fowler
Keyword(s):  
Sawtooth Oscillations
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