Non-Markovian velocity diffusion in plasma turbulence

Thesis/Dissertation · Fri Dec 31 04:00:00 EST 1993

OSTI ID:136322

Xia, H

The generalized Langevin equation, a stochastic differential equation, is derived by the projection operator method, and is applied to evaluate the diffusion coefficient in velocity space in an electrostaic plasma turbulence. The random fluctuation field is assumed to be a Gaussian and wide sense stationary process. The derived time-dependent velocity diffusion coefficients includes the resonance broadening term and retarded turbulent collision term which both contribute to the memory effect of the wave-particle interaction. Test particle experiments are carried out by following trajectories of charged particles in Langmuir turbulence. A statistical average over employed particles is used to calculate the velocity diffusion coefficient. The intrisic non-Markovian effects such as the resonance broadening and retarded turbulent collisions together with the effect of boundary layers of resonances bring departure of the diffusion coefficient from the quasilinear value. The proposed non-Markovian formulation explains the departure of the numerically observed diffusion rate from the prediction of the quasilinear theory and even from the prediction of the extended resonance broadening theory.

• Research Organization: Texas Tech Univ., Lubbock, TX (United States)
• OSTI ID: 136322
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DIFFUSION
LANGEVIN EQUATION
LINE BROADENING
PLASMA
TURBULENCE