Finite β destabilization of long-wavelength drift mode in tokamaks

2000 ◽  
Vol 78 (4) ◽  
pp. 277-283 ◽  
Author(s):  
A Hirose ◽  
M Elia
Keyword(s):  
Integral Equation ◽  
Magnetic Pressure ◽  
Mode Frequency ◽  
Larmor Radius ◽  
Mixing Length ◽  
Finite Larmor Radius ◽  
Long Wavelength ◽  
Radius Parameter ◽  
O 10 ◽  
Toroidal Geometry

Analysis based on integral equation formalism in the ballooning space indicates that in toroidal geometry, extremely long-wavelength modes with the ion finite Larmor radius parameter (k[Formula: see text]ρ)2 [Formula: see text] O(10-2) and mode frequency of the order of the ion transit frequency can be strongly destabilized by a finite β (the ratio of plasma to magnetic pressure). In high β regimes, a resultant mixing length thermal diffusivity is linearly proportional to β. PACS Nos.: 52.65Tt, 52.55Fa, 52.35Py

Nonlinear theory of large-mode-number ballooning modes in fully toroidal geometry

1985 ◽  
Vol 34 (1) ◽  
pp. 143-161 ◽  
Author(s):  
J. P. Mondt ◽  
J. Weiland
Keyword(s):  
Dispersion Relation ◽  
Aspect Ratio ◽  
Model Equation ◽  
Larmor Radius ◽  
Low Density ◽  
Magnetic Shear ◽  
Explosive Instability ◽  
Finite Larmor Radius ◽  
Special Case ◽  
Toroidal Geometry

A nonlinear model equation describing ballooning modes for β of the order of the inverse aspect ratio and including magnetic shear is derived. For the special case of circular concentric flux surfaces, we obtain an approximate dispersion relation, including finite Larmor radius effects, and show the possibility of explosive instability in the nonlinear regime. The results are shown to remain valid in the presence of a low-density hot-ion constituent.

Gyro-average method for global gyrokinetic particle simulation in realistic tokamak geometry

2022 ◽  
Author(s):  
Yihao Duan ◽  
Yong Xiao ◽  
Zhihong Lin
Keyword(s):  
Average Method ◽  
Particle Simulation ◽  
New Method ◽  
Linear Growth Rate ◽  
Larmor Radius ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Finite Larmor Radius ◽  
Long Wavelength ◽  
Orthogonal Coordinates

Abstract Gyro-average is a crucial operation to capture the essential finite Larmor radius effect (FLR) in gyrokinetic simulation. In order to simulate strongly shaped plasmas, an innovative multi-point average method based on non-orthogonal coordinates has been developed to improve the accuracy of the original multi-point average method in gyrokinetic particle simulation. This new gyro-average method has been implemented in the gyrokinetic toroidal code (GTC). Benchmarks have been carried out to prove the accuracy of this new method. In the limit of concircular tokamak, ion temperature gradient (ITG) instability is accurately recovered for this new method and consistency is achieved. The new gyro-average method is also used to solve the gyrokinetic Poisson equation, and its correctness has been confirmed in the long wavelength limit for realistic shaped plasmas. The improved GTC code with the new gyro-average method has been used to investigate the ITG instability with EAST magnetic geometry. The simulation results show that the correction induced by this new method in the linear growth rate is more significant for short wavelength modes where the finite Larmor radius (FLR) effect becomes important. Due to its simplicity and accuracy, this new gyro-average method can find broader applications in simulating the shaped plasmas in realistic tokamaks.

Analysis of electromagnetic instabilities parallel to the magnetic field

1971 ◽  
Vol 6 (1) ◽  
pp. 1-17 ◽  
Author(s):  
W. Pilipp ◽  
H. J. Völk
Keyword(s):  
Magnetic Field ◽  
Cyclotron Frequency ◽  
Larmor Radius ◽  
Collisionless Shocks ◽  
Transverse Waves ◽  
Homogeneous Plasma ◽  
Finite Larmor Radius ◽  
Long Wavelength ◽  
The Earth ◽  
The Magnetic Field

Transverse waves and instabilities propagating along the magnetic field in a homogeneous plasma are discussed analytically and numerically for frequencies of the order of the ion cyclotron frequency and below. The free energy driving the instabilities is assumed to be provided by thermal anisotropies, with the parallel temperature exceeding the perpendicular temperature, a situation appropriate to the solar wind near the earth and to the downstream conditions in collisionless shocks propagating approximately parallel to the magnetic field. It is shown that in the case where the ion β is of order one the long wavelength Firehose instability is not stabilized by finite Larmor radius effects, but that for smaller wavelengths it goes over smoothly into the resonant proton mode, discussed by Kennel & Scarf (1968).

Excitation of Alfvén waves by fast particles in a finite pressure plasma of adiabatic traps

1978 ◽  
Vol 20 (1) ◽  
pp. 137-148 ◽  
Author(s):  
B. I. Meerson ◽  
A. B. Mikhallovskii ◽  
O. A. Pokhotelov
Keyword(s):  
Uniform Magnetic Field ◽  
Alfven Waves ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Trapped Particles ◽  
Resonance Effects ◽  
Finite Larmor Radius ◽  
Pressure Plasma ◽  
Pressure Stabilization ◽  
Instability Growth

Resonant excitation of Alfvén waves by fast particles in a finite pressure plasma in a non-uniform magnetic field is studied. Plasma compressibility in the wave field is determined both by the curvature of the magnetic lines of force and finite Larmor radius of fast particles. A general expression for the instability growth rate is obtained and analyzed; the applicability of the results obtained in the previous paper has also been studied. The finite pressure stabilization of the trapped particles instability has been found. The bounce-resonance effects are analyzed.

scholarly journals Diffusion at the Earth magnetopause: enhancement by Kelvin-Helmholtz instability

2007 ◽  
Vol 25 (1) ◽  
pp. 271-282 ◽  
Author(s):  
R. Smets ◽  
G. Belmont ◽  
D. Delcourt ◽  
L. Rezeau
Keyword(s):  
Magnetic Field ◽  
Distribution Functions ◽  
Larmor Radius ◽  
Simple Analytical Model ◽  
Helmholtz Instability ◽  
Field Reversal ◽  
Finite Larmor Radius ◽  
The Earth ◽  
Specific Distribution ◽  
The Magnetic Field

Abstract. Using hybrid simulations, we examine how particles can diffuse across the Earth's magnetopause because of finite Larmor radius effects. We focus on tangential discontinuities and consider a reversal of the magnetic field that closely models the magnetopause under southward interplanetary magnetic field. When the Larmor radius is on the order of the field reversal thickness, we show that particles can cross the discontinuity. We also show that with a realistic initial shear flow, a Kelvin-Helmholtz instability develops that increases the efficiency of the crossing process. We investigate the distribution functions of the transmitted ions and demonstrate that they are structured according to a D-shape. It accordingly appears that magnetic reconnection at the magnetopause is not the only process that leads to such specific distribution functions. A simple analytical model that describes the built-up of these functions is proposed.

Finite-Larmor-radius stabilization of the m = 2 instability in the Isar T1-B high-beta stellarator

1977 ◽  
Vol 17 (1) ◽  
pp. 3-11 ◽  
Author(s):  
J. Neuhauser ◽  
M. Kaufmann ◽  
H. Röhr ◽  
G. Schramm
Keyword(s):  
Larmor Radius ◽  
Finite Larmor Radius ◽  
High Beta
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