Saturation of cosmic-ray-driven field amplification at fast shocks
In plain words
Cosmic rays streaming ahead of a shock can amplify the magnetic field, which helps trap particles and accelerate them to higher energy. How strong the amplified field becomes, which decides whether supernova remnants can accelerate protons to about $10^{15}$ electron volts, is unsettled.
Precise statement
Cosmic-ray-current-driven instabilities (notably the nonresonant Bell instability) amplify the upstream field of fast shocks. Determine the saturated amplitude $deltaB/B_{0}$ and its coherence length as functions of shock speed $v_{\mathrm{sh}}$ and cosmic-ray acceleration efficiency, including the saturation mechanism (expansion of current-driven cavities, back-reaction on the cosmic rays, nonlinear damping). An answer is $deltaB/B_{0}(v_{sh}, efficiency)$ from kinetic or hybrid simulations converged over many growth times, with an analytic saturation model from which the maximum proton energy at young supernova remnants follows.
What would settle it
Kinetic simulations resolving saturation over many growth times, consistent with field strengths inferred from the thin X-ray rims of young supernova remnants.
Results
No results have been posted on this problem yet.
Post a result · how results are checked
Sign in to follow or save this problem
Comments (0)
Comments are not records: they are not signed, stamped or logged. How comments work
No comments yet.
Sign in to comment.