A map of UHECRs deflections through the turbulent GMF

We study the effect of the random part of the Galactic Magnetic Field (GMF) on the propagation of ultra high-energy cosmic rays. We are able to derive a clear and direct relation between the observed variance of rotation measures and the predicted cosmic ray deflections, which puts a solid upper limit of the experimentally observed displacements. Remarkably, this is obtained bypassing entirely the detailed knowledge of the magnetic properties of the turbulent plasma, and that of the electron density variance. Over most of the sky the random deflections for 40 EeV protons do not exceed 1–2°, and can be as large as 5° close to the Galactic plane.