Effects of the galactic magnetic field upon large scale anisotropies of extragalactic Cosmic Rays

Abstract

The large scale pattern in the arrival directions of extragalactic cosmic rays that reach the Earth is different from that of the flux arriving to the halo of the Galaxy as a result of the propagation through the galactic magnetic field. Two different effects are relevant in this process: deflections of trajectories and (de)acceleration by the electric field component due to the galactic rotation. The deflection of the cosmic ray trajectories makes the flux intensity arriving to the halo from some direction to appear reaching the Earth from another direction. This applies to any intrinsic anisotropy in the extragalactic distribution or, even in the absence of intrinsic anisotropies, to the dipolar Compton-Getting anisotropy induced when the observer is moving with respect to the cosmic rays rest frame. For an observer moving with the solar system, cosmic rays traveling through far away regions of the Galaxy also experience an electric force coming from the relative motion (due to the rotation of the Galaxy) of the local system in which the field can be considered as being purely magnetic. This produces small changes in the particles momentum that can originate large scale anisotropies even for an isotropic extragalactic flux.

11 pages, 4 figures

References in corpus (5)

• Anisotropy and Corotation of Galactic Cosmic Rays
• The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro
• Evolution of the cosmic ray anisotropy above 10^{14} eV
• Signatures of the transition from galactic to extragalactic cosmic rays
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• Anisotropies of ultra-high energy cosmic rays diffusing from extragalactic sources
• Progress in high-energy cosmic ray physics
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• Cosmic Magnetic Lenses
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