Measurements of the Dispersion Relation of the Low-Frequency Ion Acoustic Instability in the Turbulently Heated TRIAM-1 Tokamak Plasma

1981 ◽  
Vol 20 (1) ◽  
pp. L41-L44
Author(s):  
Osamu Mitarai ◽  
Takechiyo Watanabe ◽  
Yukio Nakamura ◽  
Kazuo Nakamura ◽  
Naoji Hiraki ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Low Frequency ◽  
Tokamak Plasma ◽  
Acoustic Instability ◽  
Ion Acoustic

Local kinetic analysis of low-frequency electrostatic modes in tokamaks

1991 ◽  
Vol 69 (2) ◽  
pp. 102-106
Author(s):  
A. Hirose
Keyword(s):  
Dispersion Relation ◽  
Kinetic Analysis ◽  
Low Frequency ◽  
Acoustic Mode ◽  
Landau Damping ◽  
Trapped Electrons ◽  
Ion Acoustic ◽  
Transit Frequency

Analysis, based on a local kinetic dispersion relation in the tokamak magnetic geometry incorporating the ion transit frequency and trapped electrons, indicates that modes with positive frequencies are predominant. Unstable "drift"-type modes can have frequencies well above the diamagnetic frequency. They have been identified as the destabilized ion acoustic mode suffering little ion Landau damping even when [Formula: see text].

An assessment of how a combination of shears, field-aligned currents and collisions affect F-region ionospheric instabilities

2007 ◽  
Vol 73 (1) ◽  
pp. 69-88 ◽  
Author(s):  
J.-P. ST.-MAURICE ◽  
J.-M. NOËL ◽  
P. J. PERRON
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Theoretical Framework ◽  
Fluid Limit ◽  
Ambient Magnetic Field ◽  
Acoustic Instability ◽  
F Region ◽  
Ion Acoustic ◽  
Depth Study ◽  
Zero Frequency

Abstract.We present an in depth study of the fluid limit of a kinetically derived collisional, current-driven instability that includes shears in the field-aligned currents as well as collisions. We show how the theory presented here generalizes other theories, including the collisionless current-driven electrostatic ion acoustic instability and its sheared collisionless version. We offer a low-frequency generalization of the zero frequency ion shear driven instability by minimizing the relative drift magnitude as well as the shears themselves. We discuss the implication of our theoretical framework both for strongly field-aligned modes and modes where the wavevectors have arbitrary angles with respect to the ambient magnetic field. We discuss the results in terms of F-region irregularity observations of coherent echoes by ionospheric radars.

Dispersion relation for the lowest mode of the ion-acoustic instability in a high-current ion laser

2001 ◽  
Vol 46 (4) ◽  
pp. 400-403 ◽  
Author(s):  
V. I. Donin ◽  
V. A. Ivanov ◽  
D. V. Yakovin
Keyword(s):  
Dispersion Relation ◽  
High Current ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Ion Laser

Low-frequency instabilities of a warm plasma in a magnetic field: Part 1. Instabilities driven by field-aligned currents

1977 ◽  
Vol 17 (1) ◽  
pp. 105-122 ◽  
Author(s):  
Dean F. Smith ◽  
Joseph V. Hollweg
Keyword(s):  
Magnetic Field ◽  
Stability Analysis ◽  
Low Frequency ◽  
Marginal Stability ◽  
Numerical Techniques ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Warm Plasma ◽  
The Stability ◽  
Thermal Speed

The marginal stability of a plasma carrying current along the static magnetic field with isotropic Maxwellian ions and isotropic Maxwellian electrons drifting relative to the ions is investigated. The complete electromagnetic dispersion relation is studied using numerical techniques; the electron sums are restricted to three terms which limits the analysis to frequencies much less than the electron gyro-frequency, but includes frequencies somewhat above the ion gyro-frequency. A ‘kink-like’ instability and an instability of the Alfvén mode are found to have the lowest threshold drift velocities in most cases. In fact the threshold drift for the kink-like instability can be significantly less than the ion thermal speed. Electrostatic and electromagnetic ion-cyclotron instabilities are also found as well as the electro-static ion-acoustic instability. No instability of the fast magnetosonic mode was found. The stability analysis provides only threshold drift velocities and gives no information about growth rates.

scholarly journals Studies of Spectral Broadening of the Lower Hybrid Wave Line in the Current-Drive Regimes and Ion Heating at the FT-2 Tokamak

2021 ◽  
Vol 47 (4) ◽  
pp. 329-336
Author(s):  
V. V. Dyachenko ◽  
A. B. Altukhov ◽  
E. Z. Gusakov ◽  
L. A. Esipov ◽  
A. N. Konovalov ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Current Drive ◽  
Lower Hybrid ◽  
Ion Heating ◽  
Lower Hybrid Wave ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Lower Hybrid Current Drive ◽  
High Frequency Waves

Abstract The experiments at the FT-2 tokamak are described that were focused on clearing up the role of the parametric decay instabilities in decreasing the generation efficiency of the non-inductive current excited by the electromagnetic waves in the lower hybrid frequency range. The most discussed instability of such kind is the decay of the pump wave into the daughter high-frequency waves and the low-frequency ion–acoustic quasi-modes. The studies performed have shown that, under conditions of the FT-2 experiment, the ion–acoustic instability has no decisive effect on the decrease in the efficiency of the lower hybrid current drive.

A linear and quasi-linear investigation of the crossfield current-driven ion-acoustic instability

1982 ◽  
Vol 28 (2) ◽  
pp. 267-279 ◽  
Author(s):  
R. Bharuthram ◽  
M. A. Hellberg
Keyword(s):  
Linear Growth ◽  
Velocity Distribution Function ◽  
Linear Growth Rate ◽  
Particle Diffusion ◽  
Anomalous Resistivity ◽  
Heating Rates ◽  
Ion Heating ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Drift Instability

The linear growth rate of the crossfield current-driven ion-acoustic instability is obtained for any equilibrium particle velocity distribution function of the type . Quasi-linear theory is then used to investigate the saturation of the instability. Several associated features, namely, particle diffusion in velocity space, anomalous resistivity, energy distribution and electron and ion heating rates are evaluated for a Maxwellian distribution. Finally, a brief comparison is made with the heating rates associated with the electron cyclotron drift instability.

scholarly journals Brief Communication: The double layer in the separatrix region during magnetic reconnection

2015 ◽  
Vol 22 (2) ◽  
pp. 167-171
Author(s):  
J. Guo ◽  
B. Yu
Keyword(s):  
Electron Beam ◽  
Magnetic Reconnection ◽  
Double Layer ◽  
Particle In Cell ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Evolution Stage ◽  
Spatial Size ◽  
Electron Holes ◽  
Observation Results

Abstract. With two-dimensional (2-D) particle-in-cell (PIC) simulations we investigate the evolution of the double layer (DL) driven by magnetic reconnection. Our results show that an electron beam can be generated in the separatrix region as magnetic reconnection proceeds. This electron beam could trigger the ion-acoustic instability; as a result, a DL accompanied with electron holes (EHs) can be found during the nonlinear evolution stage of this instability. The spatial size of the DL is about 10 Debye lengths. This DL propagates along the magnetic field at a velocity of about the ion-acoustic speed, which is consistent with the observation results.

Ion-cyclotron modes in weakly relativistic plasmas

1994 ◽  
Vol 51 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Chandu Venugopal ◽  
P. J. Kurian ◽  
G. Renuka
Keyword(s):  
Dispersion Relation ◽  
High Frequency ◽  
Low Frequency ◽  
Dispersion Relations ◽  
The Other ◽  
Larmor Radius ◽  
Relativistic Plasmas ◽  
Ion Plasma ◽  
Maxwellian Plasma ◽  
Relativistic Dispersion

We derive a dispersion relation for the perpendicular propagation of ioncyclotron waves around the ion gyrofrequency ω+ in a weaklu relaticistic anisotropic Maxwellian plasma. These waves, with wavelength greater than the ion Larmor radius rL+ (k⊥ rL+ < 1), propagate in a plasma characterized by large ion plasma frequencies (). Using an ordering parameter ε, we separated out two dispersion relations, one of which is independent of the relativistic terms, while the other depends sensitively on them. The solutions of the former dispersion relation yield two modes: a low-frequency (LF) mode with a frequency ω < ω+ and a high-frequency (HF) mode with ω > ω+. The plasma is stable to the propagation of these modes. The latter dispersion relation yields a new LF mode in addition to the modes supported by the non-relativistic dispersion relation. The two LF modes can coalesce to make the plasma unstable. These results are also verified numerically using a standard root solver.

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