title: Low energy cosmic ray positron fraction explained by charge-sign dependent solar modulation.
abstract: We compute cosmic ray (CR) nuclei, proton, antiproton, electron, and positron spectra below 1 TeV at Earth by means of a detailed transport description in the galaxy and in the solar system. CR spectra below 10 GeV are strongly modified by charge-sign dependent propagation effects. These depend on the polarity of the solar magnetic field and therefore vary with the solar cycle. The puzzling discrepancy between the low-energy positron fraction measured by PAMELA and AMS-01 is then easily explained by their different data-taking epochs. We reproduce the observed spectra of CR light nuclei within the same galactic and solar-system propagation model.
authors.affiliation: Ludwig-Maximilians-Universität, Arnold Sommerfeld Center, Theresienstraße 37, D-80333 München, Germany.
authors.forename: Luca
authors.initials: L
authors.lastname: Maccione