On the origin of observed cosmic ray spectrum below 100 TV

TL;DR

This paper proposes that a local shock, possibly from Epsilon Eridani, reaccelerates cosmic rays below 50 TV, creating a spectral bump observed in recent measurements, and provides a simple model to explain all CR species spectra below 100 TV.

Contribution

The paper introduces a universal shock reacceleration model that explains the observed cosmic ray spectral bump below 100 TV using only two parameters derived from proton data.

Findings

A local shock can produce the spectral bump in cosmic rays below 50 TV.

The model accurately reproduces spectra of various CR species and the B/C ratio.

Epsilon Eridani is a plausible shock candidate responsible for the reacceleration.

Abstract

Recent precise measurements of primary and secondary cosmic rays (CRs) in the TV rigidity domain have unveiled a bump in their spectra, located between 0.5-50 TV. We argue that a local 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 (ISM) 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 from 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, Eq. (9), 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.