文章基本信息

标题：Cosmic-Ray Acceleration in Centaurus A
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作者：F.M. Rieger
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2010
卷号：2010
出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The apparent clustering of ultra-high energy cosmic-ray (UHECR) events along Cen A has attracted considerable attention within recent years. We analyze the potential of classical acceleration mechanisms to produce UHECR particles under conditions expected for Cen A. Mechanisms discussed include DC electric field acceleration in the vicinity of the black hole, first-order Fermi acceleration at internal shocks in the jet and stochastic particle acceleration in the giant radio lobes. The results indicate that: (1) Efficient acceleration of protons to Ec = 51019 eV and beyond remains challenging and most likely requires the operation of an additional mechanism capable of boosting energetic seed protons up by a factor of 10. It is proposed that shear acceleration along the large-scale jet in Cen A could be a promising candidate for this. (2) Heavier elements, such as iron nuclei, are more easily accelerated (by, e.g., shocks or direct electrostatic fields) and may not need additional boosting to reach E Ec. Observations may therefore reflect the contributions of more than one mechanism. (3) If Cen A indeed proves to be an UHECR emitting source, one may expect the cosmic-ray composition to become heavier above energies of a few times 1019 eV.