Abstract Details
Abstracts
Author: Diego del-Castillo-Negrete
Requested Type: Poster
Submitted: 2019-02-22 18:17:24
Co-authors: J. Martinell and N. Kryukov
Contact Info:
Oak Ridge National Laboratory
MS 6160
Oak Ridge, TN 37831
USA
Abstract Text:
Transport of test particles in drift-wave weak turbulence is studied using a reduced model that incorporates finite Larmor radius effects by gyro-averaging the electrostatic potential. Of particular interest is the role of gyro-averaging on the statistics of particle transport in the quasilinear limit. Numerical results show that for a thermal (Maxwellian) distribution of Larmor radii the probability distribution function (PDF) of particle displacements is Gaussian in the limit of small thermal gyro-radius but becomes strongly non-Gaussian as the thermal gyro-radius increases. However, despite the non-Gaussian shape of the PDF, the time evolution of the second moment exhibits diffusive scaling. An explanation for this behavior is presented along with analytical models for the effective diffusivity and the non-Gaussian PDF that compare very well with the numerical data. When a shear flow is added in the direction of the wave propagation, a modified model is obtained that produces free-streaming particle trajectories in addition to trapped trajectories that give rise to a novel super-ballistic transport regime.
[1] Kryukov, Martinell and D. del-Castillo-Negrete, J. Plasma Phys. 84 905840301 (2018).
Comments:
