Transport processes of high-energy cosmic rays in the interstellar medium

• Applicant: Professor Dr. Dieter Breitschwerdt
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263050076

Cosmic rays (CRs) are energetic particles that arrive on Earth in a continuous stream. The main component (90%) is represented by protons, with the rest being alpha particles (<= 10%), electrons, and heavier nuclei. The acceleration mechanisms of the CR particles with the highest energies known is still largely unknown, partly because the sources have not yet been identified. Correlations with AGNs in the local universe are still uncertain, also because of the low number density of such high-energy particles.It is the aim of this project to investigate the scattering of highest-energy CR particles in the turbulent electromagnetic fields of the interstellar medium (ISM). We will evaluate the transport processes of particles with various masses, ranging from electrons to iron nuclei. This will address the problem of a possible deflection and isotropization of extra-galactic CRs and the energy threshold (i.e., the Hillas limit) up to which this is possible.For this purpose numerical magneto-hydrodynamical (MHD) simulations of the ISM will be performed. They will provide insight into the evolution of MHD turbulence driven by supernova-induced shock waves. The transport of CRs will be investigated using two different approaches: (i) test-particles will be injected into the simulation cube and their trajectories are traced during the evolution of the magnetized medium; (ii) based on magnetic field correlation parameters from the MHD simulation Monte-Carlo simulations with a test-particle code will be carried out.The combination of independent methods will allow for a critical judgment of the assumptions used in the investigations and will therefore increase the reliability of the obtained transport parameters. Answering the questions of the origin of high-energy CRs will not only allow for an increased understanding of the nature of the most energetic particles known, but will also help the understanding of magnetic turbulence in general.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1573: Physics of the Interstellar Medium