  A nonresonant cosmic-ray-current-driven instability may operate in the shock
precursors of young supernova remnants and be responsible for magnetic-field
amplification, plasma heating and turbulence. Earlier simulations demonstrated
magnetic-field amplification, and in kinetic studies a reduction of the
relative drift between cosmic rays and thermal plasma was observed as
backreaction. However, all published simulations used periodic boundary
conditions, which do not account for mass conservation in decelerating flows
and only allow the temporal development to be studied. Here we report results
of fully kinetic Particle-In-Cell simulations with open boundaries that permit
inflow of plasma on one side of the simulation box and outflow at the other
end, hence allowing an investigation of both the temporal and the spatial
development of the instability. Magnetic-field amplification proceeds as in
studies with periodic boundaries and, observed here for the first time, the
reduction of relative drifts causes the formation of a shock-like compression
structure at which a fraction of the plasma ions are reflected. Turbulent
electric field generated by the nonresonant instability inelastically scatters
cosmic rays, modifying and anisotropizing their energy distribution. Spatial CR
scattering is compatible with Bohm diffusion. Electromagnetic turbulence leads
to significant nonadiabatic heating of the background plasma maintaining bulk
equipartition between ions and electrons. The highest temperatures are reached
at sites of large-amplitude electrostatic fields. Ion spectra show
supra-thermal tails resulting from stochastic scattering in the turbulent
electric field. Together, these modifications in the plasma flow will affect
the properties of the shock and particle acceleration there.
