  Kinetic diffusion of cosmic rays ahead of perpendicular shocks induces charge
non-neutrality, which is mostly, yet not completely, screened by the bulk
plasma via polarization drift current. Hydrodynamic shear instabilities as well
as modified Buneman instability of the polarization current generate the
turbulence necessary for a Fermi-type acceleration. Thus, similar to the case
of parallel shocks, in perpendicular shocks the diffusing cosmic rays generate
unstable plasma currents that in turn excite turbulence. This allows a
self-consistent evolution of a shock-cosmic rays system. In the kinetic regime
of the modified Buneman instability, electrons may be heated in the cosmic ray
precursor.
