The mass composition of cosmic rays measured with LOFAR

¹ Department of Astrophysics, IMAPP, Radboud University Nijmegen P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
² NIKHEF, Science Park Amsterdam, Amsterdam 1098 XG, The Netherlands
³ Astrophysical Institute, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium
⁴ ASTRON, Postbus 2, Dwingeloo 7990 AA, The Netherlands
⁵ Max-Planck-Institut für Radio Astronomie, Bonn, Germany
⁶ KVI-CART, Groningen University, P.O. Box 72, Groningen 9700 AB, The Netherlands
⁷ Interuniversity Institute for High Energies, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
⁸ now at: Department of Physics and Astronomy, University of California Irvine, Irvine, CA 92697-4575, USA
⁹ now at: Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
¹⁰ now at: Department of Physics and Electrical Engineering Linneuniversitetet, 35195 Växjö, Sweden

^a e-mail: j.horandel@astro.ru.nl-http://particle.astro.ru.nl

Published online: 23 March 2017

Abstract

High-energy cosmic rays, impinging on the atmosphere of the Earth initiate cascades of secondary particles, the extensive air showers. The electrons and positrons in the air shower emit electromagnetic radiation. This emission is detected with the LOFAR radio telescope in the frequency range from 30 to 240 MHz. The data are used to determine the properties of the incoming cosmic rays. The radio technique is now routinely used to measure the arrival direction, the energy, and the particle type (atomic mass) of cosmic rays in the energy range from 10¹⁷ to 10¹⁸ eV. This energy region is of particular astrophysical interest, since in this regime a transition from a Galactic to an extra-galactic origin of cosmic rays is expected. For illustration, the LOFAR results are used to set constraints on models to describe the origin of high-energy cosmic rays.