"Cosmic-ray acceleration at, and non-thermal emission from, supernova remnants"

Presented by Dr. Martin Pohl, Professor, from the Universitat Potsdam, Germany

Observations have established supernova remnants (SNRs) as efficient accelerators of cosmic rays, in particular electrons. Whereas the acceleration process is known in principle, many aspects are poorly understood. In fact, a number of central points that were  considered certain twenty years ago have since had to be discarded. It is still unclear how the soft production spectrum required by the observed spectrum of cosmic rays can be achieved or whether SNRs are able to accelerate protons to the ‘knee’at about 3 PeV.  Most SNRs are created in core-collapse explosions and expand into the wind bubble of their progenitor stars. This circumstellar medium (CSM) features a complex spatial distribution of gas and magnetic field that strongly affects and modifies key ingredients for particle acceleration, such as particle injection and confinement, shock conditions, and acceleration
efficiency.

The colloquium presents recent insights on the impact of the CSM on the resulting cosmic-ray distribution, derived using the RATPaC software that is designed for the time-dependent and spatially resolved modeling of particle acceleration and transport in SNRs. It is based on the simultaneous and self-consistent treatment of the SNR hydrodynamics, particle transport and magnetic turbulence.  I will also discuss the unstable isotope 60Fe, with a half-life of
2.6 million years, that is produced primarily in supernova explosions.  The observed presence of $^{60}$Fe in cosmic rays suggests an origin in the local bubble.