University of Maryland
4:30 PM Monday, February 5, 2024
Talk Recording

Mikhail A. Malkov
Dept. of Astronomy and Astrophysics, University of San Diego

Unavoidably Local Origin of the 10-TeV CR Bump

Recent measurements of primary and secondary CR spectra, their arrival directions, and our improved knowledge of the magnetic field geometry around the heliosphere allow us to set a bound on the distance beyond which a puzzling 10-TeV “bump” can not originate. The sharpness of the spectral breaks associated with the bump, the abrupt change of the CR intensity across the local magnetic equator (pitch angle), and the similarity between the primary and secondary CR spectral patterns point to a local reacceleration of the bump particles out of the background CR. We argue that a nearby shock may generate such a bump by increasing the rigidity of the preexisting CRs below 50 TV by a mere factor of ∼1.5. Reaccelerated particles below ∼0.5 TV are convected with the interstellar medium flow and do not reach the Sun, thus creating the bump. This single universal process is responsible for the observed spectra of all CR species in the rigidity range below 100 TV. We propose that one viable shock candidate is the Epsilon Eridani star at 3.2 pc of the Sun, which is well aligned with the direction of the local magnetic field. Other shocks, such as old supernova shells, may produce a similar effect. 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. We show how our formalism predicts helium and carbon spectra and the B/C ratio.