April 15-17

Abstract Details

files Add files

Abstracts

Author: Fabio Camilo de Souza
Requested Type: Poster
Submitted: 2019-02-22 09:49:09

Co-authors: N. Gorelenkov, E. Fredrickson, A. Elfimov

Contact Info:
Princeton Plasma Physics Laboratory, USA / Univers
100 Stellarator Road
Princeton, NJ   08540
United States

Abstract Text:
Geodesic Acoustic Mode (GAM) is primarily an electrostatic oscillation with the dominant toroidal N=0 and poloidal M=0,1 mode numbers. First predicted within the magnetohydrodynamic (MHD) theory [1], it's frequency is proportional to the square root of the adiabatic index gamma. GAMs can be treated by the kinetic theory, to include such parameters as the plasma rotation of different species [2], fast ions with bump-on-tail like [3] or slowing down [4] distribution function, and other models, to investigate the plasma equilibrium conditions.

NOVA [5] is an ideal MHD code that computes the Alfvénic and acoustic continua and eigenmodes. The adiabatic index in NOVA is a fixed parameter, typically 5/3. The acoustic oscillations are calculated using the prescribed gamma value and its coupling with others continua.

As in kinetic calculations it is possible to include other effects for more accuracy of the GAM continuum. We modified NOVA to include a profile for gamma, given as a function of the magnetic surfaces. This modification makes the MHD acoustic continuum to match the Kinetic one. This kinetic gamma allows to compute more accurate eigenmodes which are strongly coupled to GAM continuum structure. This conclusion is similar to all low frequency oscillations including GAMs, the Alfvén-acoustic BAAE modes and others. The understanding of the impact of discharge parameters in these modes can improve the plasma transport control.

Simulation results for NSTX and DIII-D, changes in the continuum and eigenmodes frequency and localization, will be presented. Implications to the experiments on those machines will be discussed.

[1] N. Winsor, et. al., Phys. Fluids 11, 2448 (1968)
[2] A.G. Elfimov, et. al., Phys. Plasmas 22, 114503 (2015)
[3] F. Camilo de Souza, et. al, Phys. Lett. A 381, 3066 (2017)
[4] Z. Qiu, et. al., Plasma Phys. Controlled Fusion 52, 095003 (2010)
[5] C. Z. Cheng and M. S. Chance, Journal of Computational Phys., 71, 124-146 (1987)

Comments:
Plasma Properties, Equilibrium, Stability, and Transport
Computer Simulation of Plasmas