Research Letters

Cosmic ray propagation in a fractal galactic medium

Hamid A. Kermani, Jalileldin Fatemi
South African Journal of Science | Vol 107, No 1/2 | a275 | DOI: https://doi.org/10.4102/sajs.v107i1/2.275 | © 2011 Hamid A. Kermani, Jalileldin Fatemi | This work is licensed under CC Attribution 4.0
Submitted: 13 May 2010 | Published: 24 January 2011

About the author(s)

Hamid A. Kermani, Department of Physics, Faculty of Science, University of Kerman, Islamic Republic of Iran
Jalileldin Fatemi, Department of Physics, Faculty of Science, University of Kerman, Islamic Republic of Iran

Abstract

Simple cosmic ray diffusion in magnetic fields is often discussed in terms of a characteristic scattering mean free path or equivalent diffusion coefficient. This assumes very simple properties of the structure of astrophysical magnetic fields. A better approximation is to assume that the magnetic structure has fractal properties and there is then the possibility of including very short and very long interaction lengths when modelling the propagation. Results of modelling such propagation in a fractal medium are discussed. Values of the propagation parameter (α) less than 2 were obtained and confirm the plausibility of the hypothesis that supernova are the origin of galactic cosmic rays in the energy range below the knee in the spectrum.

Keywords

cosmic ray; diffusion; fractal; magnetic field

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