Tripolar vortices in ion-temperature-gradient mode with non-Maxwellian electrons in an inhomogeneous magnetoplasma

2017 ◽  
Vol 95 (7) ◽  
pp. 650-654
Author(s):  
Anisa Qamar ◽  
Javed Iqbal ◽  
U. Zakir ◽  
Arshad M. Mirza
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Low Frequency ◽  
Equilibrium Density ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Field Gradients ◽  
Frequency Plasma ◽  
Magnetic Field Gradients ◽  
Kappa Distributed Electrons

We consider a low frequency plasma comprising of Kappa distributed electrons and Maxwellian ions embedded in an external magnetic field in toroidal ion-temperature-gradient driven modes. A set of nonlinear equations are derived in the presence of equilibrium density, temperature, and magnetic field gradients. In the nonlinear regime, solutions in the form of tripolar vortices are derived by using Braginskii’s transport equations. It has been observed that the scale lengths over which the nonlinear vortex structures form get modified in the presence of Kappa distributed electrons. In tokamak the present study is applicable where non-Maxwellian population has been observed in electron cyclotron heating experiments and resonant frequency heating.

Formation of dipolar vortices and vortex streets due to nonlinearly interacting ion-temperature-gradient-driven modes in dense magnetoplasmas

2010 ◽  
Vol 77 (2) ◽  
pp. 245-255 ◽  
Author(s):  
NAZIA BATOOL ◽  
ARSHAD M. MIRZA
Keyword(s):  
Temperature Gradient ◽  
Nonlinear Equations ◽  
Spatial Scales ◽  
Low Frequency ◽  
Equilibrium Density ◽  
Quantum Plasma ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Vortex Streets ◽  
Magnetic Field Gradients

AbstractNonlinear equations which govern the dynamics of low-frequency (ω ⪡ ωci, where ω is the perturbation frequency of the wave and ωci is the ion gyro-frequency), ion-temperature-gradient-driven modes in the presence of equilibrium density, temperature and magnetic field gradients are derived. New set of nonlinear equations are derived. In the nonlinear case, new types of solutions in the form of dipolar vortices and vortex streets are found to exist in dense quantum plasma. These structures are found to be formed on very short spatial scales.

Low-frequency fluctuations in scrape-off layer of tokamak plasma with limiter biasing

2011 ◽  
Vol 77 (6) ◽  
pp. 733-748
Author(s):  
N. BISAI ◽  
RAMESWAR SINGH ◽  
R. SINGH
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Tokamak Plasma ◽  
Equilibrium Density ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Electron Temperature Gradient ◽  
Field Mobility

AbstractThe effects of limiter biasing on the equilibrium density and potential profiles of the scrape-off layer (SOL) in tokamak plasma are investigated by including ionization and cross-field mobility. It is shown that a broadening of SOL can take place by the inclusion of ionization for low negative biasing. Various microinstabilities relevant for SOL plasmas have been studied. Generalized low-frequency dispersion relation is derived. It is shown that limiter biasing significantly modifies the SOL fluctuations. It is also shown that growth rate of conductive wall instability is smaller for negative biasing than positive biasing case. New mode, the modified Simon–Hoh, and ion temperature gradient instabilities are found to contribute significantly to the growth of curvature- and electron temperature-gradient-driven conductive wall instabilities.

scholarly journals Fully Kinetic Simulation of Ion-Temperature-Gradient Instability in Tokamaks

2018 ◽  
Author(s):  
Youjun Hu ◽  
Matthew T. Miecnikowski ◽  
Yang Chen ◽  
Scott E. Parker
Keyword(s):  
Temperature Gradient ◽  
Time Scale ◽  
Low Frequency ◽  
Magnetic Configuration ◽  
Short Time Scale ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Cyclotron Motion ◽  
Drift Motion ◽  
Variational Integrator

The feasibility of using full ion kinetics, instead of gyrokinetics, in simulating low-frequency Ion-Temperature-Gradient (ITG) instabilities in tokamaks has recently been demonstrated by Sturdevant et al. [Physics of Plasmas 24, 081207 (2017)]. In that work, a variational integrator was developed to integrate the full orbits of ions in toroidal geometry, which proved to be accurate in capturing both the short-time scale cyclotron motion and long time scale drift motion. The present work extends that work in three aspects. First, we implement a relatively simple full orbit integrator, the Boris integrator, and demonstrate that the accuracy of this integrator is also sufficient for simulation of ITG instabilities. Second, the equilibrium magnetic configuration is extended to general toroidal configuration specified numerically, enabling simulation of realistic equilibria reconstructed from tokamak experiments. Third, we extend that work to the nonlinear regime and investigate the nonlinear saturation of ITG instabilities. To verify the new numerical implementation of the orbit integrator and magnetic configuration, the linear electrostatic ITG frequency and growth rate are compared with those given in Sturdevant's work and good agreement is found.

scholarly journals Fully Kinetic Simulation of Ion-Temperature-Gradient Instabilities in Tokamaks

Plasma ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Youjun Hu ◽  
Matthew Miecnikowski ◽  
Yang Chen ◽  
Scott Parker
Keyword(s):  
Temperature Gradient ◽  
Time Scale ◽  
Low Frequency ◽  
Momentum Conservation ◽  
Nonlinear Regime ◽  
Short Time Scale ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Cyclotron Motion ◽  
Drift Motion

The feasibility of using full ion kinetics, instead of gyrokinetics, in simulating low-frequency Ion-Temperature-Gradient (ITG) instabilities in tokamaks has recently been demonstrated. The present work extends the full ion kinetics to the nonlinear regime and investigates the nonlinear saturation of a single-n ITG instability due to the E × B trapping mechanism (n is the toroidal mode number). The saturation amplitude predicted by the E × B trapping theory is found to agree with the saturation level observed in the simulation. In extending to the nonlinear regime, we developed a toroidal Boris full orbit integrator, which proved to be accurate in capturing both the short-time scale cyclotron motion and long time scale drift motion, with good kinetic energy conservation and toroidal angular momentum conservation in tokamak equilibrium magnetic fields. This work also extends the previous work from analytic circular magnetic equilibria to general numerical magnetic equilibria, enabling simulation of realistic equilibria reconstructed from tokamak experiments.

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