The MHD continuum with a radial electric field

Könies, Axel; Slaby, C.; Kleiber, R.; Fehér, Tamás; Borchardt, M.; Mishchenko, A.

doi:10.1063/5.0023961

Cited by 9 publications

(9 citation statements)

References 43 publications

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“…One can see that the frequency remains at the toroidicity-induced gap for all times of the nonlinear evolution. The shear-Alfvén continuum is computed using the CONTI code [18,19] within the slowsound approximation.…”

Section: Alfvén Eigenmodes In the Presence Of Fast Ions And Electroma...mentioning

confidence: 99%

Gyrokinetic particle-in-cell simulations of electromagnetic turbulence in the presence of fast particles and global modes

Mishchenko,

Bottino,

Hayward-Schneider

et al. 2022

Preprint

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Global simulations of electromagnetic turbulence, collisionless tearing modes, and Alfvén Eigenmodes in the presence of fast particles are carried out using the gyrokinetic particle-in-cell codes ORB5 (E. Lanti et al, Comp. Phys. Comm, 251, 107072 (2020)) and EUTERPE (V. Kornilov et al, Phys. Plasmas, 11, 3196 (2004)) in tokamak and stellarator geometries. Computational feasibility of simulating such complex coupled systems is demonstrated.

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Section: Alfvén Eigenmodes In the Presence Of Fast Ions And Electroma...mentioning

confidence: 99%

Gyrokinetic particle-in-cell simulations of electromagnetic turbulence in the presence of fast particles and global modes

Mishchenko,

Bottino,

Hayward-Schneider

et al. 2022

Preprint

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“…Another possibility one may consider is to use a precomputed damping rate γ d (r, ω) that depends on radius and frequency, for instance using a gyrokinetic solver for the plasma dispersion relation, such as LIGKA [63,64]. Moreover, it has been shown that radial electric fields can also have an impact on the structure of Alfvén continua in the frequency range of interest [65] and, thus, may affect chirping dynamics.…”

Section: Appendix D Characterization and Verification Of The Model D1 Background Plasma Responsementioning

confidence: 99%

On the Effect of Beating during Nonlinear Frequency Chirping

Bierwage

Roscoe

Duarte

2021

Plasma and Fusion Research

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Spectroscopic analyses of energetic particle (EP) driven bursts of MHD fluctuations in magnetically confined plasmas often exhibit chirps that occur simultaneously in groups of two or more. While the superposition of oscillations at multiple frequencies necessarily causes beating in the signal acquired by a localized external probe, self-consistent hybrid simulations of chirping EP modes in a JT-60U tokamak plasma have demonstrated the possibility of global beating, where the mode's electromagnetic field vanishes globally between beats and reappears with opposite phase [Bierwage et al., Nucl. Fusion 57, 016036 (2017)]. This implies that there can be a single coherent field mode that oscillates at multiple frequencies simultaneously when it is resonantly driven by multiple density waves in EP phase space. Conversely, this means that the EP density waves are mutually coupled and interfere with each other via the jointly driven field, a mechanism ignored in some theories of chirping. In this thesis-style treatise, we study the role of field pulsations in general and beating in particular using the Hamiltonian guiding center orbit-following code ORBIT with a reduced wave-particle interaction model in realistic geometry. Beating is found to drive the evolution of EP phase space structures. A key mechanism is the pulsation of effective phase space islands combined with the alternation of their effective O-and X-points due to phase jumps between each beat. Observations: (1) Beating causes density wave fronts to advance radially in a pulsed manner and the resulting chirps become staircase-like. (2) The pulsations facilitate convective transfer of material between neighboring layers of phase space density waves. On the one hand, this may inhibit the early detachment of solitary phase space vortices. On the other hand, it facilitates the accumulation of hole and clump fragments into larger structures. (3) Long-range chirping is observed when massive holes or clumps detach and drift away from the turbulent belt around the seed resonance. It is remarkable that the detached vortices remain robust and, on average, maintain their concentric nested layers while being visibly perturbed by the field's continued beating.

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“…Another possibility one may consider is to use a precomputed damping rate γ d (r, ω) that depends on radius and frequency, for instance using a gyrokinetic solver for the plasma dispersion relation, such as LIGKA [57,58]. Moroever, it has been shown that radial electric fields can also have an impact on the structure of Alfvén continua in the frequency range of interest [59] and, thus, may affect chirping dynamics. The condition dG/dt = 0 underlying our implementation of the δ f method, namely Eq.…”

Section: C4 Ghost Chirps and Resonance Overlapmentioning

confidence: 99%

On the effect of beating during nonlinear frequency chirping

Bierwage,

White,

Duarte

2021

Preprint

View full text Add to dashboard Cite

Spectroscopic analyses of energetic particle (EP) driven bursts of MHD fluctuations in magnetically confined plasmas often exhibit chirps that occur simultaneously in groups of two or more. While the superposition of oscillations at multiple frequencies necessarily causes beating in the signal acquired by a localized external probe, self-consistent hybrid simulations of chirping EP modes in a JT-60U tokamak plasma have demonstrated the possibility of global beating, where the mode's electromagnetic field vanishes globally between beats and reappears with opposite phase. This implies that there can be a single coherent field mode that oscillates at multiple frequencies simultaneously when it is resonantly driven by multiple density waves in EP phase space. Conversely, this means that the EP density waves are mutually coupled and interfere with each other via the jointly driven field, a mechanism ignored in some theories of chirping. In this thesis-style treatise, we study the role of field pulsations in general and beating in particular using the Hamiltonian guiding center orbit-following code ORBIT with a reduced wave-particle interaction model in realistic geometry. Beating is found to be a mechanism that drives the evolution of EP phase space structures: (1) Beating causes density wave fronts to advance radially in a pulsed manner, initiating staircase-like chirps. (2) The pulsations facilitate convective transfer of material between neighboring layers of phase space density waves. On the one hand, this may inhibit the early detachment of solitary phase space vortices. On the other hand, it facilitates the accumulation of hole and clump fragments into larger structures. (3) Long-range chirping is observed when massive holes or clumps detach and drift away from the turbulent belt around the seed resonance. It is remarkable that the detached vortices remain robust and, on average, maintain their concentric nested layers while being visibly perturbed by the field's continued beating.

show abstract

The MHD continuum with a radial electric field

Cited by 9 publications

References 43 publications

Gyrokinetic particle-in-cell simulations of electromagnetic turbulence in the presence of fast particles and global modes

Gyrokinetic particle-in-cell simulations of electromagnetic turbulence in the presence of fast particles and global modes

On the Effect of Beating during Nonlinear Frequency Chirping

On the effect of beating during nonlinear frequency chirping

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