Physics
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........39d&link_type=abstract
Thesis (PH.D.)--PRINCETON UNIVERSITY, 1993.Source: Dissertation Abstracts International, Volume: 54-10, Section: B, page: 5218.
Physics
28
Landau Damping
Scientific paper
Turbulence in magnetized plasma in the presence of density, velocity, and temperature gradients is studied numerically and analytically with an extended fluid model. Interactions between plasma waves and plasma particles are considered in the low-frequency limit (omega<< eB/mic). The unique feature of the model is a set of fluid closure relations for the moments of the electrostatic gyrokinetic equation. The resulting set of fluid equations contain approximate models that describe Landau damping and its inverse ( omega~ k_| v_{ti }), the usual finite-Larmor-radius effects (k_{|rho_i}~ 1), and a new, nonlinear perpendicular phase-mixing effect (~ k_sp {|}{2}|Phi_ {vec{k}}vec{k} times vec{k}^'|) due to the finite Larmor radii. The equations are investigated linearly both locally and nonlocally, analytically and numerically. Nonlinearly, a local weak -turbulence calculation is carried out for electron drift -wave turbulence. A nonlinear, three-dimensional gyrofluid code is described for the study of the turbulent transport resulting from pressure gradients in a plasma embedded in a strong, sheared magnetic field. Thermal transport properties are measured and compared to existing particle simulation results and to modern magnetic fusion tokamak experiments. It is found that the gyrofluid model compares favorably with gyrokinetic particle simulations, lending credence to the various approximations employed. Physics results from gyrofluid simulations indicate that the thermal transport associated with pressure gradients in a simple (sheared but without curvature) magnetic-field geometry is not sufficient to explain the anomalous transport observed in magnetic confinement fusion devices. However, it is found that the interaction between the fluctuations and the self-generated flows often dominate the nonlinear dynamics, even when the flows themselves are not large compared to the turbulent fluctuations. It is expected that this interplay, previously ignored for turbulence characteristic of the core plasma in a thermonuclear fusion reactor, will persist in the presence of curvature and magnetic drifts. Finally, it is noted that the inclusion of toroidal drift resonances could destabilize the system further, making this turbulence relevant to existing experiments.
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