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

Abstract

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. 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 differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

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Affiliated Institutions

• Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas ES
• National Central University TW
• Institute of Electrical Engineering CN
• Institut National de Physique Nucléaire et de Physique des Particules FR
• University of Milano-Bicocca IT
• National Aeronautics and Space Administration US
• Yale University US
• Laboratoire d’Annecy de Physique des Particules FR
• Laboratoire de Physique Subatomique et de Cosmologie FR
• Ewha Womans University KR
• Institute of High Energy Physics CN
• Middle East Technical University TR
• University of Geneva CH
• Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca IT
• Karlsruhe Institute of Technology DE
• LIP - Laboratory of Instrumentation and Experimental Particle Physics PT
• Istituto Nazionale di Fisica Nucleare, Sezione di Bologna IT
• University of Turku FI
• Istituto Nazionale di Fisica Nucleare, Sezione di Perugia IT
• RWTH Aachen University DE
• Istituto Nazionale di Fisica Nucleare, Sezione di Roma I IT
• Centre National de la Recherche Scientifique FR
• Université Grenoble Alpes FR
• Instituto de Astrofísica de Canarias ES
• University of Bologna IT
• University of Trento IT
• Chinese Academy of Sciences CN
• Istituto Nazionale di Fisica Nucleare, Trento Institute for Fundamental Physics And Applications IT
• Southeast University CN
• University of Perugia IT
• Jülich Aachen Research Alliance DE
• Massachusetts Institute of Technology US
• Johnson Space Center US
• Sapienza University of Rome IT
• European Organization for Nuclear Research CH
• University of Pisa IT
• Institute of Physics, Academia Sinica TW
• Shandong University CN
• Istituto Nazionale di Fisica Nucleare, Sezione di Pisa IT
• University of Hawaii System US

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