Nonlinear saturation of whistler modes driven by runaway electrons
Runaway electrons exhibit kinetic instabilities with potentially beneficial consequences. The anomalous Doppler resonance between the electrons and whistler modes is a primary underlying mechanism. These instabilities require a first-principle nonlinear theoretical analysis, which would ultimately enable assessment of their impact on disruption mitigation and diagnostics, especially in ITER-relevant conditions. This paper presents recent progress in developing the required theoretical framework for isolated nonlinear resonances. By employing the generic bump-on-tail model, we predict the wave saturation levels in both near-threshold and strongly driven regimes. Remarkably, for the waves of interest, the parallel component of the wave vector dictates the parallel momentum of the resonant particles. This feature, together with the expected wave saturation level, provides a complete description of the resonance impact on the runaway electron distribution function. We show that the parametric dependence of the nonlinearly saturated mode provides a way to recover certain features of the runaway momentum distribution function.
- Research Organization:
- The University of Texas at Austin; Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies
- Sponsoring Organization:
- U.S. Department of Energy; USDOE Office of Science (SC)
- Grant/Contract Number:
- FG02-04ER54742; SC0016283
- OSTI ID:
- 1991970
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 30; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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