Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 42: Nuclear and Particle Astrophysics III

HK 42.8: Vortrag

Donnerstag, 11. März 2004, 15:45–16:00, F

Diffusive shock acceleration at oblique shocks — •Athina Meli and Peter Biermann — Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, 53121, Bonn, Germany

Our aim here is to evaluate the rate of the maximum energy and the acceleration rate that particles acquire in the non-relativistic diffusive shock acceleration as it could apply during their lifetime in various astrophysical sites. We examine numerically (using Monte Carlo simulations) the effect of the diffusion coefficients on the energy gain and the acceleration rate, by testing the role between the obliquity of the magnetic field at the shock normal, and the significance of both perpendicular (cross-field diffusion) and parallel diffusion coefficients. We find (and justify previous analytical work) that if there is a highly oblique shock, the smaller the perpendicular diffusion gets compared to the parallel diffusion coefficient values, the greater the energy gain of the cosmic rays to be obtained. An explanation of the cosmic ray spectrum between 10 and 10¹⁸eV is claimed, as we estimate the upperlimit of energy that cosmic rays could gain in the plausible regimes where conditions such as magnetic obliquity and diffusion coefficients ‘limited’ ratio and -most importantly- time limitsshould apply.