Analytic stability boundaries for compressional and global Alfven eigenmodes driven by fast ions. II. Interaction via Landau resonance.

Lestz, J. B. ; Gorelenkov, N. N. ; Belova, E. V. ; Tang, S. X. ; Crocker, N. A.
Issue date: 2020
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Lestz, J. B., Gorelenkov, N. N., Belova, E. V., Tang, S. X., & Crocker, N. A. (2020). Analytic stability boundaries for compressional and global Alfven eigenmodes driven by fast ions. II. Interaction via Landau resonance [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.11578/1608306
@electronic{lestz_j_b_2020,
  author      = {Lestz, J. B. and
                Gorelenkov, N. N. and
                Belova, E. V. and
                Tang, S. X. and
                Crocker, N. A.},
  title       = {{Analytic stability boundaries for compre
                ssional and global Alfven eigenmodes dri
                ven by fast ions. II. Interaction via La
                ndau resonance.}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2020,
  url         = {https://doi.org/10.11578/1608306}
}
Description:

Conditions for net fast ion drive are derived for beam-driven, co-propagating, sub-cyclotron compressional (CAE) and global (GAE) Alfven eigenmodes driven by the Landau resonance with super-Alfvenic fast ions. Approximations applicable to realistic neutral beam distributions and mode characteristics observed in spherical tokamaks enable the derivation of marginal stability conditions for these modes. Such conditions successfully reproduce the stability boundaries found from numerical integration of the exact expression for local fast ion drive/damping. Coupling between the CAE and GAE branches of the dispersion due to finite \omega/\omega_{ci} and k_\parallel/k_\perp is retained and found to be responsible for the existence of the GAE instability via this resonance. Encouraging agreement is demonstrated between the approximate stability criterion, simulation results, and a database of NSTX observations of co-CAEs.

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