Probing Local ISM Turbulence by High-Fidelity Measurements of Cosmic Rays*

Recent measurements of the cosmic ray (CR) energy spectrum, angular distribution, and chemical composition offer new insights into the magnetic turbulence through which they propagate. The new data unveil a “bump” at 10 TeV that comprises two sharp spectral breaks, an abrupt change in the CR intensity across the local magnetic horizon (90^○ CR pitch angle), and the similarity between the primary and secondary CR spectral patterns, which all points to a local reacceleration of the bump particles out of the omni-galactic CRs. We argue that the most viable candidate for the bump production is the ε -Eridani star at 3.2 pc of the Sun, which is well aligned with the direction of the local magnetic field. We provide a simple formula that reproduces the spectra of all CR species with only two nonadjustable shock parameters uniquely derived from the proton data. Since the source of the bump is only a few m.f.p away from the Sun, it has an imprint of turbulence to which it has been exposed en route. We argue that accurately fitting the data to the propagation model requires an Iroshnikov-Kraichnan k^-3/2 spectrum. We discuss a mechanism of its self-generation by the bump CRs propagating through an over-pressured magnetic flux tube.