Time Dependence of the Electron and Positron Components of the Cosmic Radiation Measured by the PAMELA Experiment between July 2006 and December 2015

Journal: Physical Review Letters

Published: 2016-06-17

DOI: 10.1103/physrevlett.116.241105

Affiliations: 20

Authors: 55

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Research Highlight

What PAMELA can tell us about positrons

© Science Photo Library – SCIEPRO/Brand X Pictures/Getty

© Science Photo Library – SCIEPRO/Brand X Pictures/Getty

A change in cosmic rays in 2015 compared to values taken in the 1990s has been explained by solar cycles, according to an international team including researchers from the Moscow Engineering Physics Institute.

Cosmic rays are streams of high-energy particles travelling through the Universe at almost the speed of light. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics experiment — PAMELA to its friends — looked at measurements of low-energy positrons — or ‘antimatter electrons’ — taken between 2006 and 2015.

The team found that the positron fraction in cosmic rays was much higher in 2015 than in the 1990s, and also between 2006 and 2013. This was because the Sun’s magnetic field flipped direction during 2013 and 2014 and pointed north along its rotational axis, allowing more positrons to reach PAMELA.

This finding was in agreement with theoretical models that predict how cosmic rays drift according to their charge and magnetic field.

  1. Physical Review Letters 116, 241105 (2016). doi: 10.1103/physrevlett.116.241105
Institutions FC WFC
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russia 0.20 0.20
INFN Section in Trieste, Italy 0.11 0.11
INFN Section in Florence, Italy 0.11 0.11
Department of Physics, University of Rome Tor Vergata, Italy 0.06 0.06
INFN Section in Napoli, Italy 0.06 0.06
INFN Section in Roma Tre, Italy 0.06 0.06
Ioffe Institute, RAS, Russia 0.05 0.05
P.N. Lebedev Physical Institute (LPI), RAS, Russia 0.05 0.05
INFN Section in Bari, Italy 0.05 0.05
Department of Physics, University of Siegen, Germany 0.04 0.04
Centre for Space Research, NWU, South Africa 0.04 0.04
Oskar Klein Centre for Cosmoparticle Physics (OKC), Sweden 0.04 0.04
Dipartimento Interateneo di Fisica "Michelangelo Merlin", Italy 0.03 0.03
INFN Frascati National Laboratory (LNF), Italy 0.03 0.03
Department of Physics and Astronomy, UNIFI, Italy 0.02 0.02
Institute of Applied Physics "Nello Carrara" (IFAC), CNR, Italy 0.02 0.02
Department of Physics, UNINA, Italy 0.01 0.01
Department of Mathematics and Informatics, UNIUD, Italy 0.01 0.01
ASI Science Data Center (ASDC), Italy 0.01 0.01
Department of Physics, UNITS, Italy 0.01 0.01