Electron and Positron Fluxes in Primary Cosmic Rays measured with the Alpha Magnetic Spectrometer on the International Space Station

TL;DR

This paper reports precise measurements of cosmic-ray electron and positron fluxes by AMS-02, revealing distinct energy-dependent behaviors and spectral indices that inform their origins.

Contribution

It presents the first detailed comparison of electron and positron fluxes showing different spectral behaviors above 30 GeV.

Findings

Electron and positron fluxes deviate from single power-law spectra.

Positron spectral index is harder than electron's between 20 and 200 GeV.

Different spectral behaviors suggest distinct origins for electrons and positrons.

Abstract

Precision measurements by the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station of the primary cosmic-ray electron flux and the positron flux will be discussed. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ~30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the different behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.