  We study electron heating in collisionless current-driven turbulence due to
the nonlinear interactions between electron- and ion-acoustic waves. PIC
simulation results show that due to a large difference between the electron and
ion mean velocities the Buneman instability excites large-amplitude
ion-acoustic waves, which strongly modifies the electron velocity distribution
function, leading to a secondary instability that generates fast
electron-acoustic waves; and in this process, a giant electron hole is
ultimately created. This giant electron hole is responsible for strong electron
heating due to phase mixing. The numerical simulation results are consistent
with the previous observations and provide insight into the key processes
responsible for electron heating and the generation of nonlinear waves in a
collisionless current-driven instability.
