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A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

S. Buitink 1 A. Corstanje 1 H. Falcke 1, 2 J. R. Hörandel 1 T. Huege 3 A. Nelles 1 J. P. Rachen 1 L. Rossetto 1 P. Schellart 1 O. Scholten 4 S. ter Veen 5 S. Thoudam 1 T. N. G. Trinh 6 J. Anderson 7 A. Asgekar 2 I. M. Avruch 8 M. E. Bell 9 M. J. Bentum 2 G. Bernardi P. Best 10 A. Bonafede 11 F. Breitling 12 J. W. Broderick 13 W. N. Brouw 14 M. Brüggen 11 H. R. Butcher 2 D. Carbone 15 B. Ciardi 16 J. E. Conway 17 F. de Gasperin 18 E. de Geus 19 A. Deller 2 R.-J. Dettmar 20 G. van Diepen 2 S. Duscha 2 J. Eislöffel 21 D. Engels 18 J. E. Enriquez 22 R. A. Fallows 23 R. Fender 13 C. Ferrari 24 W. Frieswijk 2 M. A. Garrett 25, 2 Jean-Mathias Grießmeier 26, 27 A. W. Gunst 2 M. P. van Haarlem 2 T. E. Hassall 28 G. Heald 2 J. W. T. Hessels 15 M. Hoeft 21 A. Horneffer 29 M. Iacobelli 25 H. Intema 25 E. Juette 30 A. Karastergiou 31 V. I. Kondratiev 2 M. Kramer 29, 32 M. Kuniyoshi 29 G. Kuper 2 J. van Leeuwen 15 G. M. Loose 2 P. Maat 2 G. Mann 33 S. Markoff 34 R. Mcfadden 2 D. Mckay-Bukowski 35 J. P. Mckean 2 M. Mevius 2 D. D. Mulcahy 13 H. Munk 2 M. J. Norden 2 E. Orru 2 H. Paas 36 M. Pandey-Pommier 37 V. N. Pandey 38 M. Pietka 39 R. Pizzo 2 A. G. Polatidis 2 W. Reich 29 H. J. A. Röttgering 25 A. M. M. Scaife 40 D. J. Schwarz 41 M. Serylak 26, 27 J. Sluman 2 O. Smirnov 42 B. W. Stappers 28 M. Steinmetz 43 A. Stewart 44 J. Swinbank 34 Michel Tagger 26 Y. Tang 45 C. Tasse 46, 47 M. C. Toribio 48 R. Vermeulen 2 C. Vocks 33 C. Vogt 2 R. J. van Weeren 2 R. A. M. J. Wijers 15 S. J. Wijnholds 2 M. W. Wise 34, 2 O. Wucknitz 49 S. Yatawatta 2 P. Zarka 50, 51 J. A. Zensus 29
1 Radboud university [Nijmegen]
2 ASTRON - Netherlands Institute for Radio Astronomy
3 Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology (
4 University of Groningen [Groningen]
5 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics
6 LAGA - Laboratoire Analyse, Géométrie et Applications
7 Institute for Mathematics Applied to Geoscience
8 SRON - SRON Netherlands Institute for Space Research
9 ATNF - Australia Telescope National Facility
10 University of Edinburgh
11 Jacobs University [Bremen]
12 AIP - Leibniz-Institut für Astrophysik Potsdam
13 University of Southampton
14 Kapteyn Astronomical Institute [Groningen]
15 UvA - University of Amsterdam [Amsterdam]
16 Max Planck Institute for Astrophysics
17 Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology
18 Hamburger Sternwarte/Hamburg Observatory
19 Medstar Research Institute
20 Astronomisches Institut der Ruhr-Universität Bochum
21 TLS - Thüringer Landessternwarte Tautenburg
22 SETI Institute
23 Institute of Mathematical and Physical Sciences
24 Département de Géologie
25 Leiden Observatory [Leiden]
26 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
27 USN - Unité Scientifique de la Station de Nançay
28 Jodrell Bank Centre for Astrophysics
29 MPIFR - Max-Planck-Institut für Radioastronomie
30 Ruhr-Universität Bochum [Bochum]
31 Oxford Astrophysics
32 CAL - Columbia Astrophysics Laboratory
33 AIP - Leibniz-Institut für Astrophysik Potsdam
34 AI PANNEKOEK - Astronomical Institute Anton Pannekoek
35 University of Oulu
36 Center for Information Technology CIT
37 CRAL - Centre de Recherche Astrophysique de Lyon
38 NRAO - National Radio Astronomy Observatory [Charlottesville]
39 University of Oxford [Oxford]
40 School of Physics and Astronomy [Southampton]
41 Interactions Son Musique Mouvement
STMS - Sciences et Technologies de la Musique et du Son
42 Rhodes University, Grahamstown
43 DSMZ - Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures
44 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
45 UP11 - Université Paris-Sud - Paris 11
46 SKA South Africa
47 GEPI - Galaxies, Etoiles, Physique, Instrumentation
48 Finca El Encin
49 AlfA - Argelander-Institut für Astronomie
50 OP - Observatoire de Paris - Site de Paris
51 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
Abstract : Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6, 7, 8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6, 12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.
Keywords : High-energy astrophysics Particle astrophysics
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Journal articles
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Contributor : Nathalie Rouchon <>
Submitted on : Tuesday, February 14, 2017 - 2:18:44 PM
Last modification on : Thursday, September 24, 2020 - 10:04:02 AM
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CNRS | UNIV-ORLEANS | UNIV-PARIS7 | OBSPM | LESIA | IRCAM | UPMC | CRAL | STMS | LAGA | UNIV-PARIS13 | INSU | USPC | UNIV-PARIS8 | UNIV-PARIS-SACLAY | UNIV-LYON1 | USN | SORBONNE-UNIVERSITE | OSUC | LPC2E | GALILE | ENS-LYON | SU-SCIENCES | UNIV-PARIS-LUMIERES | UDL | GEPI | UP-SCIENCES | PSL

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S. Buitink, A. Corstanje, H. Falcke, J. R. Hörandel, T. Huege, et al.. A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations. Nature, Nature Publishing Group, 2016, 531 (7592), pp.70-73. ⟨10.1038/nature16976⟩. ⟨insu-01321748⟩

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