Measuring a Cherenkov ring in the radio emission from air showers at 110–190MHz with LOFAR

A. Nelles (1) , P. Schellart (1) , S. Buitink (1) , A. Corstanje , K.D. de Vries (1) , J.E. Enriquez (2) , H. Falcke (3, 4, 1) , W. Frieswijk , J.R. Hörandel , O. Scholten (5) , S. ter Veen (6) , S. Thoudam (1) , M. van den Akker , J. Anderson , A. Asgekar (3) , M.E. Bell (7) , M.J. Bentum (3) , G. Bernardi (8) , P. Best (9) , J. Bregman (3) , F. Breitling (10) , J. Broderick (7) , W.N. Brouw (11) , M. Brüggen (12) , H.R. Butcher (3) , B. Ciardi (13) , A. Deller , S. Duscha , J. Eislöffel (14) , R.A. Fallows (15) , M.A. Garrett (3, 16) , A.W. Gunst (3) , T.E. Hassall (17) , G. Heald (3) , A. Horneffer , M. Iacobelli (18, 19) , E. Juette (20) , A. Karastergiou (21) , V.I. Kondratiev (3) , M. Kramer (22) , M. Kuniyoshi (4) , G. Kuper (3) , P. Maat (3) , G. Mann (10) , M. Mevius (3) , M.J. Norden , H. Paas (3) , M. Pandey-Pommier (23) , G. Pietka (21) , R. Pizzo (3) , A.G. Polatidis (3) , W. Reich (4) , H. Röttgering (16) , A.M.M. Scaife (24) , D. Schwarz , O. Smirnov (25) , B.W. Stappers (17) , M. Steinmetz (26) , A. Stewart (27) , Michel Tagger (28) , Y. Tang (29) , C. Tasse (30) , R. Vermeulen , C. Vocks , R.J. van Weeren (3) , S.J. Wijnholds (3) , O. Wucknitz (31) , S. Yatawatta (11) , P. Zarka (30)

1 Radboud University [Nijmegen]
2 SETI Institute
3 ASTRON - Netherlands Institute for Radio Astronomy
4 MPIFR - Max-Planck-Institut für Radioastronomie
5 KVI - Kernfysisch Versneller Instituut, Univ. of Groningen
6 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics
7 University of Southampton
8 CfA - Harvard-Smithsonian Center for Astrophysics
9 University of Edinburgh
10 AIP - Leibniz-Institut für Astrophysik Potsdam
11 Kapteyn Astronomical Institute [Groningen]
12 Jacobs University [Bremen]
13 Max Planck Institute for Astrophysics
14 TLS - Thüringer Landessternwarte Tautenburg
15 Institute of Mathematical and Physical Sciences
16 Leiden Observatory [Leiden]
17 Jodrell Bank Centre for Astrophysics
18 CMLS - Centre de Mathématiques Laurent Schwartz
19 Sapienza University of Rome - Dipartimento di Matematica "Guido Castelnuovo" [Roma I]
20 Ruhr-Universität Bochum [Bochum]
21 Oxford Astrophysics
22 VUMC - Vrije Universiteit Medical Centre
23 CRAL - Centre de Recherche Astrophysique de Lyon
24 School of Physics and Astronomy [Southampton]
25 Rhodes University, Grahamstown
26 DSMZ - Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures
27 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
28 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
29 SYSU - Sun Yat-Sen University [Guangzhou]
30 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
31 AlfA - Argelander-Institut für Astronomie

Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ∼100∼100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110–190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle.

Keywords: Extensive air showers; Radio emission; LOFAR; Cosmic rays; time-compression

Domains: Sciences of the Universe [physics]

A. Nelles, P. Schellart, S. Buitink, A. Corstanje, K.D. de Vries, et al.. Measuring a Cherenkov ring in the radio emission from air showers at 110–190MHz with LOFAR. Astroparticle Physics, 2015, 65, pp.11-21. ⟨10.1016/j.astropartphys.2014.11.006⟩. ⟨insu-01271487⟩