Saturation of energetic-particle-driven geodesic acoustic modes due to wave–particle nonlinearity

Biancalani, A.; Chavdarovski, I.; Qiu, Zhiyong; Bottino, A.; Sarto, D. Del; Ghizzo, A.; Gürcan, Özgür; Morel, Pierre; Novikau, I.

doi:10.1017/s0022377817000976

Cited by 18 publications

(53 citation statements)

References 53 publications

(163 reference statements)

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“…Note that the chirping of EGAM was reported in previous publications, both experimentally [7] and numerically [12]. Very recently, in global gyrokinetic simulations using the Orb5 code [28], a chirping of EGAM was also observed [29], when only wave-particle nonlinearities are kept in the gyro-kinetic equations. It was later shown in [30] that adding wave-wave nonlinearities in that case may result in the strong reduction of the chirping.…”

Section: Brief Description Of Gysela Code and Excitation And Nonlineasupporting

confidence: 61%

Particle transport due to energetic-particle-driven geodesic acoustic modes

Zarzoso¹,

del‐Castillo‐Negrete²,

Escande³

et al. 2018

Nucl. Fusion

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The transport of particles in the presence of energetic geodesic acoustic modes (EGAMs) is analysed by means of full-f global gyro-kinetic simulations using the multispecies version of the Gysela code and a test-particle tracking post-treatment that solves the equations of motion of passive gyro-centres embedded in the self-consistent EGAM potential obtained from Gysela simulations. It is found that EGAMs induce transport of particles that eventually results in counter-passing particle losses modulated at the EGAM frequency. A detailed analysis of the trajectories of test gyro-centres is performed and evidences of the interaction between the EGAM island and the region of magnetically trapped particles (trapping cone) is observed. In particular, we report for the first time on the complex interaction between the stochastic separatrix of the EGAM island and the X-point of the trapping cone, creating a channel for the transport of particles from v < 0 to v > 0 regions. Therefore, for the cases analysed in this work, co-injection of energetic particles might lead to a significant reduction of EGAM-induced losses. This result opens up new perspectives for further studies of the selection of energetic particle injection in order to minimize the losses due to EGAMs.

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Section: Brief Description Of Gysela Code and Excitation And Nonlineasupporting

confidence: 61%

Particle transport due to energetic-particle-driven geodesic acoustic modes

Zarzoso¹,

del‐Castillo‐Negrete²,

Escande³

et al. 2018

Nucl. Fusion

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“…Other interesting effects, associated with the EGAM nonlinear evolution, are the EGAM frequency chirping, which consists in a fast modification of the mode frequency, and the saturation mechanisms. Since the frequency shift during the chirping is considered to occur as a result of the wave-particle interaction [60][61][62][63][64][65] , the MPR diagnostic can be used to investigate this phenomenon as well. The saturation mechanisms (wave-particle or wave-wave interactions) are important to investigate in order to build a theoretical model capable of predicting the saturation levels in experimentally relevant conditions, and as a consequence, the EP redistribution in phase space.…”

Section: Discussionmentioning

confidence: 99%

Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space

Novikau

Biancalani

Bottino

et al. 2021

Computer Physics Communications

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A new diagnostic has been developed to investigate the wave-particle interaction in the phase-space in gyrokinetic particle-in-cell codes. Based on the projection of energy transfer terms onto the velocity space, the technique has been implemented and tested in the global code ORB5 and it gives an opportunity to localise velocity domains of maximum wave-plasma energy exchange for separate species. Moreover, contribution of different species and resonances can be estimated as well, by integrating the energy transfer terms in corresponding velocity domains. This Mode-Plasma-Resonance (MPR) diagnostic has been applied to study the dynamics of the Energetic-particle-induced Geodesic Acoustic Modes (EGAMs) in an ASDEX Upgrade shot, by analysing the influence of different species on the mode time evolution.Since the equations on which the diagnostic is based, are valid in both linear and nonlinear cases, this approach can be applied to study nonlinear plasma effects. As a possible future application, the technique can be used, for instance, to investigate the nonlinear EGAM frequency chirping, or the plasma heating due to the damping of the EGAMs.

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“…1972; Biancalani et al. 2017). As a consequence, the question arises whether also the EP redistribution in phase space can be described with similar models for both instabilities.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the scaling of the saturated electric field of EGAMs with the linear growth rate, for saturation due to wave–particle nonlinearity, has been studied with ORB5 (Biancalani et al. 2017). The BPS is studied here with a 1-D code treating the thermal plasma as a cold dielectric medium and describing the dynamics of the fast electrons as an N-body problem solved with a Hamiltonian formulation (Carlevaro et al.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear velocity redistribution caused by energetic-particle-driven geodesic acoustic modes, mapped with the beam-plasma system

et al. 2018

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The nonlinear dynamics of energetic particle (EP) driven geodesic acoustic modes (EGAM) in tokamaks is investigated, and compared with the beam-plasma system (BPS). The EGAM is studied with the global gyrokinetic (GK) particle-in-cell code ORB5, treating the thermal ions and EP (in this case, fast ions) as GK and neglecting the kinetic effects of the electrons. The wave-particle nonlinearity only is considered in the EGAM nonlinear dynamics. The BPS is studied with a 1D code where the thermal plasma is treated as a linear dielectric, and the EP (in this case, fast electrons) with an n-body hamiltonian formulation. A one-to-one mapping between the EGAM and the BPS is described. The focus is on understanding and predicting the EP redistribution in phase space. We identify here two distint regimes for the mapping: in the low-drive regime, the BPS mapping with the EGAM is found to be complete, and in the high-drive regime, the EGAM dynamics and the BPS dynamics are found to differ. The transition is described with the presence of a non-negligible frequency chirping, which affects the EGAM but not the BPS, above the identified drive threshold. The difference can be resolved by adding an ad-hoc frequency modification to the BPS model. As a main result, the formula for the prediction of the nonlinear width of the velocity redistribution around the resonance velocity is provided.

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Saturation of energetic-particle-driven geodesic acoustic modes due to wave–particle nonlinearity

Cited by 18 publications

References 53 publications

Particle transport due to energetic-particle-driven geodesic acoustic modes

Particle transport due to energetic-particle-driven geodesic acoustic modes

Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space

Nonlinear velocity redistribution caused by energetic-particle-driven geodesic acoustic modes, mapped with the beam-plasma system

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