Gyrokinetic particle simulation of fast-electron driven beta-induced Aflvén eigenmode

Abstract

The fast-electron driven beta-induced Alfv en eigenmode (e-BAE) in toroidal plasmas is investigated for the first time using global gyrokinetic particle simulations, where the fast electron is described by the drift kinetic equation. The simulation shows that the e-BAE propagates in the fast electron diamagnetic direction and its polarization is close to an ideal MHD mode. The phase space structure shows that only the fast electron processional resonance is responsible for the e-BAE excitations while fast-ion driven BAE can be excited through all the channels, including transit, bounce, and processional resonance. Published by AIP Publishing.

Nonlinear co-existence of beta-induced Alfvén eigenmodes and beta-induced Alfvén-acoustic eigenmodes

“…20 The Alfv en instabilities related to fast electrons were widely observed, such as the internal kink mode and fishbone in DIII-D, 21 BAE and fishbone in HL-2A. 22,23 The fast-electron driven BAE was identified for the first time both in Ohmic and electron cyclotron resonance heating plasma in HL-2A 23,24 and has been verified in linear simulations 25 using GTC. The BAAE is formed through the coupling of the shear Alfv en continuum and the acoustic continuum in the toroidal geometry, which was first formulated based on the magneto-hydrodynamics (MHD) approach.…”

“…5(d)] as the pure e-BAE. 25 In the nonlinear stage (point B in Fig. 4) when BAE's amplitude is nearly minimum in the oscillation process, a new mode branch emerges on the larger radius side of original BAE and it has lower rotation velocity in the h direction than the BAE branch during the evolution of mode structure (Fig.…”

“…Since the Larmor radii of electrons are much smaller compared with the characteristic spatial scale of BAE which is of the same order of the thermal ion Larmor radius, the driftkinetic limit is used for electrons 25 for simplicity while the finite Larmor effect is retained for the thermal ion. For thermal electrons, the transit frequency and bounce frequency are much higher than the BAE frequency, since the mess of electrons is very small.…”

Mode structure symmetry breaking of energetic particle driven beta-induced Alfvén eigenmode

“…4. More generally, by identifying the basic ingredient of symmetry breaking of mode structure, this work can provide an input to other perturbative/nonperturbative codes and suggest interpretation of simulation results 7,[21][22][23] .…”

Particle simulation of radio frequency waves with fully-kinetic ions and gyrokinetic electrons

“…GTC has been successfully used in studying electrostatic turbulence, energetic particle transport and Alfvén wave physics. These works include the ion temperature gradient [23] [24], electron temperature gradient [25], trapped electron mode [26], turbulence induced energetic particle (EP) transport [27], toroidicity-induced Alfvén eigenmode (TAE) [28] [29] and beta-induced Alfvén eigenmode (BAE) [30,31]. This paper will be organized as follows: the set of Vlasov-Maxwell equations for gyrokinetic electron species and fully-kinetic ion species is introduced in section 2.…”