Cosmic Magnetic Lenses

TL;DR

This paper introduces the concept of cosmic magnetic lenses, showing how certain magnetic field configurations can deflect cosmic rays in patterns similar to gravitational lenses, affecting cosmic ray observations and fluxes.

Contribution

It proposes a simple model of a cosmic magnetic lens with a constant azimuthal magnetic field, analyzing its effects on cosmic ray deflection and image formation.

Findings

Magnetic lenses can produce one, two, or four images of a point source.

Lenses can be convergent or divergent depending on magnetic field direction and cosmic ray charge.

Lenses may cause flux fluctuations and matter-antimatter asymmetries.

Abstract

Magnetic fields play a critical role in the propagation of charged cosmic rays. Particular field configurations supported by different astrophysical objects may be observable in cosmic ray maps. We consider a simple configuration, a constant azimuthal field in a disk-like object, that we identify as a cosmic magnetic lens. Such configuration is typical in most spiral galaxies, and we assume that it can also appear at smaller or larger scales. We show that the magnetic lens deflects cosmic rays in a regular geometrical pattern, very much like a gravitational lens deflects light but with some interesting differences. In particular, the lens acts effectively only in a definite region of the cosmic-ray spectrum, and it can be convergent or divergent depending on the (clockwise or counterclockwise) direction of the magnetic field and the (positive or negative) electric charge of the cosmic ray. We find that the image of a point-like monochromatic source may be one, two or four points depending on the relative position of source, observer and center of the lens. For a perfect alignment and a lens in the orthogonal plane the image becomes a ring. We also show that the presence of a lens could introduce low-scale fluctuations and matter-antimatter asymmetries in the fluxes from distant sources. The concept of cosmic magnetic lens that we introduce here may be useful in the interpretation of possible patterns observed in the cosmic ray flux at different energies.