On drift wave instabilities excited by strong plasma gradients in toroidal plasmas

Motivated by the recent global gyrokinetic simulations of electrostatic drift-wave instabilities in the strong plasma gradient region of toroidal plasmas [Fulton et al., Phys. Plasmas 21, 042110 (2014); Xie et al., Phys. Rev. Lett. 118, 095001 (2017); Xie and Xiao, Phys. Plasmas 22, 090703 (2015)], we have carried out the corresponding analytical and numerical investigations in the case of ion temperature gradient driven modes. It is shown that, for sufficiently strong plasma gradients, the eigenmodes are slab-like and predominantly bounded by the plasma non-uniformities. Our results are qualitatively consistent with the simulation observations.