Bremen 2017 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 3: Astrophysik

EP 3.1: Vortrag

Montag, 13. März 2017, 16:30–16:45, GW2 B2880

Proton and Helium Injection Into First Order Fermi Acceleration at Shocks: Hybrid Simulation and Analysis — •Adrian Hanusch¹, Mikhail Malkov², and Tatyana Liseykina¹ — ¹Universität Rostock — ²University of California, San Diego

The problem of cosmic ray (CR) origin is more than a hundred-year-old. Most likely, their acceleration occurs at collisionless shocks in supernova remnants by diffusive shock acceleration (DSA). By this mechanism, charged particles gain energy by crossing the shock front occasionally, while being scattered by magnetic perturbations in the shock vicinity.

The mechanism is physically simple and robust, but some important aspects are still not well understood. One difficulty is connected already with its start, when the shock must select a tiny fraction of particles to keep on crossing its front and gaining energy continuously. This initial phase of the DSA is referred to as “injection.” Recent measurements of PAMELA [1] and AMS-02 [2] show a difference between He²⁺ and proton spectra. The elemental composition of galactic CR might hold the key to their origin. A comparison of injection rates of particles with different mass to charge ratio is a powerful tool for studying the injection process and the DSA in general.

We performed a series of one dimensional hybrid simulations and analyzed the impact of He²⁺ admixture on the injection of both protons and helium.

[1] O. Adriani et al., Science, 332, 69 (2011).

[2] M. Aguilar et al., Phys. Rev. Lett. 115, 211101 (2015).