Full-f 6D particle-in-cell simulations of quasi-kinetic equilibrium with spatial inhomogeneity and ITG mode

We are studying the quasi-kinetic equilibrium with spatial inhomogeneity and ion temperature gradient (ITG) modes by six-dimensional (6D) full-f particle-in-cell (PIC) simulations. For the ITG mode, fluid equilibrium with spatial inhomogeneity can be established straightforwardly, but there is no known suitable analytical equilibrium that satisfies the time-independent Vlasov-Maxwell system exactly. Full-f PIC simulations with 6D ions and adiabatic electrons are carried out to search for a quasi-kinetic equilibrium with spatial inhomogeneity. The time evolution of density, ion-temperature and ion-velocity profiles are obtained, and the time-dependent ion distribution function is also numerically constructed. The frequency spectrum of the density, ion-temperature, ion-velocity, ion distribution function from the PIC simulation is compared to the timescale analysis of the dynamics of the Vlasov equation. The threshold of ITG instabilities is estimated using a fluid model for the system parameters adopted in the simulation. We plan to carry out 6D full-f PIC simulations in the unstable region predicted by the fluid model to observe the ITG instabilities.