Paper detail

Anisotropy in the cosmic radiation at TeV energy

In recent years very important results were obtained from cosmic ray experiments about the arrival direction distribution of primaries in the TeV energy range. As most of these particles are charged nuclei, they are deflected by the magnetic field they pass through before reaching the Earth surface, the effect of the Lorentz force being inversely proportional to the particle energy. As far as the local interstellar medium is known, the gyroradius of a 10 TeV proton is expected to be only 100 a.u., small enough to make the arrival direction distribution isotropic. Since 1930s a "large scale" (90°-120°) anisotropy is known to exist, generally interpreted as the combined effect of sources far away and magnetic fields nearby. Nonetheless, in the last decade experiments like Tibet-ASg, Milagro, ARGO-YBJ and IceCube discovered structures as wide as 10°-30° all over the sky at ~ 10 TeV energy, what is unexplainable within the standard model of cosmic rays. In this paper a review of the most recent experimental results about cosmic ray anisotropy is given, together with the status of the art of theoretical efforts aimed at interpreting them within the current cosmic-ray paradigma.