The existence and time evolution of charge separation at a plasma edge is
studied using a code in which both ions and electrons are described by
gyrokinetic equations that include the finite-Larmor-radius correction and the
polarization drift. The ion finite-Larmor-radius effect allows the existence of
charge separation between ions and electrons, and the polarization drift, which
has opposite signs for ions and electrons, has a tendency to accentuate the
charge separation in a time-varying electric field. We compare our results with
those previously obtained using a code in which the ions were described by
using a fluid guiding-centre model, and only the electrons were treated
kinetically. In particular, we present results showing excellent agreement
between the two codes on the transition of the spectrum of the nonlinear
solution from a turbulent spectrum to one dominated by the fundamental
mode, where the energy is condensing in the lowest-k modes (inverse cascade).