Nonlinear Radial Propagation of Drift Wave Turbulence.
We study the linear and the nonlinear radial propagation of drift wave energy in an inhomogeneous plasma. The drift mode excited in such a plasma is dispersive in nature. The drift wave energy spreads out symmetrically along the direction of inhomogeneity with a finite group velocity. To study the effect of the nonlinear coupling on the propagation of energy in a collision free plasma, we solve the Hasegawa -Mima equation as a mixed initial boundary-value problem. The solutions of the linearised equation are used to check the reliability of our numerical calculations. Additional checks are also performed on the invariants of the system. Our results reveal that a pulse gets distorted as it propagates through the medium. The peak of the pulse propagates with a finite velocity that depends on the amplitude of the initial pulse. The polarity of propagation depends on the initial parameters of the pulse. We have also studied drift wave propagation in a resistive plasma. The Hasegawa -Wakatani equations are used to investigate this problem. From the results of our numerical calculations we find that the resistive drift wave grows as it propagates through the medium. For spatially dependent resistivity the peak of the pulse propagates in the direction of decreasing resistivity. The polarity of propagation is independent of the phases of the initial pulse. We explain the results of our calculations in the framework of weak turbulence theory. These results provide qualitative insights into the phenomenon of drift wave turbulence observed in tokamak Plasmas.
- Pub Date:
- Physics: Fluid and Plasma