Development of a Fourier-space gyrokinetic eigenvalue code including magnetic mirror effects for ion-temperature-gradient modes

The magnetic mirror effects are included in the local Fourier-space gyrokinetic eigenvalue solver, ESR, to study the ion-temperature-gradient (ITG) mode in toroidal geometry. The passing-ion magnetic mirror (PIMM) effects are included by applying a poloidal Fourier decomposition to the relevant linear operators, and the trapped-ion effects are treated by solving the orbit-averaged Vlasov equation. The upgraded Fourier-space eigenvalue code ESR benchmarks well against the well-known ballooning-space eigenvalue code FULL. The instability analysis of the adiabatic electron ITG mode with the magnetic mirror effects suggests that the PIMM effects stabilize the ITG mode mainly in the high kθρi (>0.5) regime, whereas the trapped-ion effects exhibit a strong destabilizing effect mainly in the low kθρi (<0.2) regime. The magnetic mirror effects modify the ITG linear growth rate through inducing the additional toroidal coupling between the neighboring poloidal harmonics.