A quasineutral full-kinetic-ion drift-fluid-electron model forsimulation of low-frequency plasma turbulence

Fully kinetic ion models have recently garnered attention as a means to verify and extend the ubiquitous gyrokinetic models applied to studies of low-frequency plasma turbulence in tokamaks. Previous studies have had success in reproducing gyrokinetic results, particularly the growth and saturation of the ion-temperature-gradient instability, but a robust alternative to gyrokinetics in this context remains elusive due to numerical challenges associated with the quasineutral limit and the inherent multiscale nature of the problem. We present a new approach, in which the assumption of quasineutrality, along with the first moments of the kinetic equation for ions and the drift-kinetic equation for electrons, provides a soluble field equation without undesirable high-frequency solutions. As a proof of concept, we present linear and nonlinear results under the electrostatic approximation with the assumption of isothermal electrons. We favorably compare the measured linear dispersion to the full-kinetic-ion drift-kinetic electron theory and study nonlinear couplings to ion Bernstein waves and electrostatic ion cyclotron waves.