The 'PAMELA anomaly' indicates a nearby cosmic ray accelerator

TL;DR

This paper proposes that nearby supernova remnants can produce a hard electron and positron component, explaining the PAMELA positron excess and predicting related high-energy cosmic ray features.

Contribution

It introduces a model where secondary electrons and positrons from supernova remnants account for the observed cosmic ray anomalies, incorporating stochastic uncertainties.

Findings

Predicts a dominant high-energy component from supernova remnants

Successfully fits the PAMELA positron fraction rise

Foresees a high-energy increase in the B/C ratio

Abstract

We discuss the recently observed `excesses' in cosmic ray electron and positron fluxes which have been widely interpreted as signals of dark matter. By considering the production and acceleration of secondary electrons and positrons in nearby supernova remnants, we predict an additional, harder component that becomes dominant at high energies. The unknown spatial distribution of the supernova remnants introduces a stochastic uncertainty which we estimate analytically. Fitting the prediction for different source distributions to the total electron + positron flux measured by Fermi--LAT fixes all free parameters and allows us to `postdict' the rise in the positron fraction seen by PAMELA. A similar rise in the B/C ratio is predicted at high energies.