U.S. Department of EnergyOffice of Scientific and Technical Information
Energetic-particle-modified global Alfven eigenmodes
Abstract
Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfven eigenmodes (GAE) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function -- the normalized injection velocity v_0/v_A and central pitch -- are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v_0/v_A. This unexpected result is present for both counter-propagating GAEs, which are routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in mode structure could indicate the existence of a new energetic particle mode, referred to here as an energetic-particle-modified GAE (EP-GAE). Additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.
- Authors:
- Publication Date:
- DOE Contract Number:
- AC02-09CH11466
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- U. S. Department of Energy
- OSTI Identifier:
- 1562074
- DOI:
- https://doi.org/10.11578/1562074
Citation Formats
Lestz, J B, Belova, E V, and Gorelenkov, N N. Energetic-particle-modified global Alfven eigenmodes. United States: N. p., 2017.
Web. doi:10.11578/1562074.
Lestz, J B, Belova, E V, & Gorelenkov, N N. Energetic-particle-modified global Alfven eigenmodes. United States. doi:https://doi.org/10.11578/1562074
Lestz, J B, Belova, E V, and Gorelenkov, N N. 2017.
"Energetic-particle-modified global Alfven eigenmodes". United States. doi:https://doi.org/10.11578/1562074. https://www.osti.gov/servlets/purl/1562074. Pub date:Fri Dec 01 00:00:00 EST 2017
@article{osti_1562074,
title = {Energetic-particle-modified global Alfven eigenmodes},
author = {Lestz, J B and Belova, E V and Gorelenkov, N N},
abstractNote = {Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfven eigenmodes (GAE) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function -- the normalized injection velocity v_0/v_A and central pitch -- are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v_0/v_A. This unexpected result is present for both counter-propagating GAEs, which are routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in mode structure could indicate the existence of a new energetic particle mode, referred to here as an energetic-particle-modified GAE (EP-GAE). Additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.},
doi = {10.11578/1562074},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Dec 01 00:00:00 EST 2017},
month = {Fri Dec 01 00:00:00 EST 2017}
}