Parity-breaking parametric decay instability of kinetic Alfvén waves in a nonuniform plasma

Chen, Liu; Qiu, Zhiyong; Zonca, F.

doi:10.1063/5.0091057

Cited by 6 publications

(9 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The particle responses can be derived by separating the linear from nonlinear components by taking δH k = δH L k,j + δH NL k,j , with the superscripts 'L' and 'NL' denoting the linear and nonlinear responses, respectively. It is noteworthy that, in the WKB limit, the present analysis is quite similar to that of [47] for parametric decay of KAWs in nonuniform plasma, with differences due to the peculiar features associated with toroidal geometry.…”

Section: Parametric Decay Instabilitysupporting

confidence: 72%

Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay

Cheng,

Shen,

Qiu

2024

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

The parametric decay of toroidal Alfvén eigenmode (TAE) in nonuniform plasmas is investigated using nonlinear gyrokinetic equation. It is found that, the plasma nonuniformity not only significantly enhances the nonlinear coupling cross-section, but also qualitatively modifies the decay process. Specifically, the condition for spontaneous decay becomes the toroidal mode number of the sideband TAE being higher than that of the pump TAE, instead of the frequency of the sideband TAE being lower than the pump TAE in uniform plasmas. The consequences on TAE saturation and energetic particle transport are also discussed.

show abstract

Section: Parametric Decay Instabilitysupporting

confidence: 72%

Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay

Cheng,

Shen,

Qiu

2024

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…In this work, we assume the nonlinear coupling is dominated by thermal plasma contribution, while EPs, driving the pump RSAE unstable, contribute negligibly to the nonlinear coupling. Consequently, the nonuniformity of thermal plasma in the tokamak core can be neglected [44], corresponding to thermal ion diamagnetic drift frequency being smaller than BAE frequency here, in consistency with the considered highperformance scenarios [18]. Thus, the present theory, which could be generalized to included kinetic ballooning modes (KBMs) [13] and/or Alfvénic ion temperature gradient modes (AITGs) [23,45] by inclusion of thermal plasma nonuniformities, is derived for application to BAE in its present form.…”

Section: Theoretical Modelmentioning

confidence: 66%

Core localized alpha-channeling via low frequency Alfvén mode generation in reversed shear scenarios

Wei¹,

Wang²,

Chen³

et al. 2022

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

A novel channel for fuel ions heating in tokamak core plasma is proposed and analyzed using nonlinear gyrokinetic theory. The channel is achieved via spontaneous decay of reversed shear Alfvén eigenmode (RSAE) into low frequency Alfvén modes (LFAM), which then heat fuel ions via collisionless ion Landau damping. The conditions for RSAE spontaneous decay are investigated, and the saturation level and the consequent fuel ion heating rate are also derived. The channel is expected to be crucial for future reactors operating under reversed shear configurations, where fusion alpha particles are generated in the tokamak core with the magnetic shear being, typically, reversed, and there is a dense RSAE spectrum due to the small alpha particle characteristic dimensionless orbits.

show abstract

“…Technol. 26 (2024) 053001 T Wang et al netic vorticity equation derived from the parallel Ampère's law, quasi-neutrality condition and nonlinear gyrokinetic equation [2,130,131]. The first two equations read…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Here, the three terms on the left hand side (LHS) of the vorticity equation ( 3) denote the field line bending, inertia, and the curvature coupling, respectively. The two terms on the RHS are formally nonlinear and correspond to MX and RS, respectively [131].…”

Section: Theoretical Modelmentioning

confidence: 99%

“…The spontaneous excitation of ZFZS by a pump wave was firstly considered for drift and drift-Alfvén waves as a paradigm case [131], and then extended for TAE [51] and BAE [139]. It was shown that for the TAE, the generation of zonal magnetic field, i.e., zonal current (ZC) is dominant over the electrostatic zonal flow (ZF), mainly due to the magnetically trapped-ion enhanced polarizability [62].…”

Section: Modulational Instability and The Generation Of Zfzsmentioning

confidence: 99%

See 1 more Smart Citation

Nonlinear dynamics of the reversed shear Alfvén eigenmode in burning plasmas

WANG 王,

WEI 魏,

BRIGUGLIO

et al. 2024

Plasma Sci. Technol.

Self Cite

View full text Add to dashboard Cite

In a tokamak fusion reactor operated at steady state, the equilibrium magnetic field is likely to have reversed shear in the core region, as the noninductive bootstrap current profile generally peaks off-axis. The reversed shear Alfvén eigenmode (RSAE) as a unique branch of the shear Alfvén wave in this equilibrium, can exist with a broad spectrum in wavenumber and frequency, and be resonantly driven unstable by energetic particles (EP). After briefly discussing the RSAE linear properties in burning plasma condition, we review several key topics of the nonlinear dynamics for the RSAE through both wave-EP resonance and wave-wave coupling channels, and illustrate their potentially important role in reactor-scale fusion plasmas. By means of simplified hybrid MHD-kinetic simulations, the RSAEs are shown to have typically broad phase space resonance structure with both circulating and trapped EP, as results of weak/vanishing magnetic shear and relatively low frequency. Through the route of wave-EP nonlinearity, the dominant saturation mechanism is mainly due to the transported resonant EP radially decoupling with the localized RSAE mode structure, and the resultant EP transport generally has a convective feature. The saturated RSAEs also undergo various nonlinear couplings with other collective oscillations. Two typical routes as parametric decay and modulational instability are studied using nonlinear gyrokinetic theory, and applied to the scenario of spontaneous excitation by a finite amplitude pump RSAE. Multiple RSAEs could naturally couple and induce the spectral energy cascade into a low frequency Alfvénic mode, which may effectively transfer the EP energy to fuel ions via collisionless Landau damping. Moreover, zero frequency zonal field structure could be spontaneously excited by modulation of the pump RSAE envelope, and may also lead to saturation of the pump RSAE by both scattering into stable domain and local distortion of the continuum structure.

show abstract

Parity-breaking parametric decay instability of kinetic Alfvén waves in a nonuniform plasma

Cited by 6 publications

References 37 publications

Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay

Effects of plasma nonuniformity on toroidal Alfvén eigenmode nonlinear decay

Core localized alpha-channeling via low frequency Alfvén mode generation in reversed shear scenarios

Nonlinear dynamics of the reversed shear Alfvén eigenmode in burning plasmas

Contact Info

Product

Resources

About