Investigation of the diurnal variation of cosmic rays at large latitudes by the detectors of the Extreme Energy Events Project

Abstract The diurnal modulation in galactic cosmic ray flux observed on the Earth is a widely studied phenomenon. Most of the analyses of this effect have been undertaken with data obtained by neutron monitor stations distributed over the world. The effect may also be seen in muon detectors, although muons are affected in a different way than neutrons. Particularly interesting is a comparison between the data obtained from neutron stations and muon telescopes located in the same region. In this paper we report an investigation of the diurnal modulation of cosmic rays at large latitudes, based on the data collected by three scintillator telescopes of the EEE (Extreme Energy Events) Project, installed at Ny-Ålesund, in the Svalbard archipelago, at $$79^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>79</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> N, during the period 2019–2025. Amplitudes and phases of the observed diurnal maximum in the cosmic ray flux were extracted in various periods by a harmonic fit of the averaged daily trend. Muon results were also compared to data collected in the period 2003–2025 by the Barentsburg Neutron Monitor Station, located not far from our detectors. The data, integrated along periods of one year, with a moving average in six months steps, show evidence of a diurnal modulation, with amplitudes of (0.05−0.1) $$\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>%</mml:mo> </mml:math> , smaller, roughly by a factor 2, than for neutrons, and a phase generally close to 12–16 h local time. No sensible differences were observed in the anisotropy parameters between solar nights and days in the polar region. The possible contribution of a second harmonic in the observed diurnal trend was also investigated.

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Journal
The European Physical Journal C
Published
2026-06-25
DOI
https://doi.org/10.1140/epjc/s10052-026-15901-y
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

Investigation of the diurnal variation of cosmic rays at large latitudes by the detectors of the Extreme Energy Events Project

F. Gramegna, L. Votano, C. Pellegrino, D. Hatzifotiadou et al.
The European Physical Journal C
Astrophysics and Cosmic Phenomena
article

Investigation of the diurnal variation of cosmic rays at large latitudes by the detectors of the Extreme Energy Events Project

F. Gramegna, L. Votano, C. Pellegrino, D. Hatzifotiadou, E. Coccia, A. Margotti, G. Maron, C. Vistoli, A. Trifirò, M. Trimarchì, M. Battaglieri, L. Quaglia, R. Paoletti, L. Galante, F. Nozzoli, R. Nania, G. Scioli, A. De, C. Avanzini, P. La Rocca, F. Palmonari, S. De Pasquale, F. Riggi, R. Zuyeuski, S. Grazzi, C. Cicalò, D. Cavazza, E. Gramstad, F. Carnesecchi, G. Mandaglio, M. Taiuti, C. Pinto, M. Garbini, M. Selvi, Giancarlo C. Righini, E. Scapparone, A. Corvaglia, K. Piscicchia, C. Ripoli, D. De Gruttola, L. Baldini, F. Noferini, L. Cifarelli, M. Panareo, Bianca Sabiu, F. Ould-Saada, A. Mulliri, S. Pisano, M. N. Mazziotta, O. Pinazza, G. Batignani, I. Gnesi, M.C.S. Williams, E. Bossini, F. Coccetti, G. Sartorelli, A. Scribano, M. Abbrescia, M. Schioppa, E. S. Håland, L Perasso, M. Rasa, M. P. Panetta, M. Rizzi, L. E. Ghezzer, R. Liotino, R. Baldini Ferroli, A. Zichichi, D. Piccolo
article en

Abstract

Abstract The diurnal modulation in galactic cosmic ray flux observed on the Earth is a widely studied phenomenon. Most of the analyses of this effect have been undertaken with data obtained by neutron monitor stations distributed over the world. The effect may also be seen in muon detectors, although muons are affected in a different way than neutrons. Particularly interesting is a comparison between the data obtained from neutron stations and muon telescopes located in the same region. In this paper we report an investigation of the diurnal modulation of cosmic rays at large latitudes, based on the data collected by three scintillator telescopes of the EEE (Extreme Energy Events) Project, installed at Ny-Ålesund, in the Svalbard archipelago, at $$79^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>79</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> N, during the period 2019–2025. Amplitudes and phases of the observed diurnal maximum in the cosmic ray flux were extracted in various periods by a harmonic fit of the averaged daily trend. Muon results were also compared to data collected in the period 2003–2025 by the Barentsburg Neutron Monitor Station, located not far from our detectors. The data, integrated along periods of one year, with a moving average in six months steps, show evidence of a diurnal modulation, with amplitudes of (0.05−0.1) $$\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>%</mml:mo> </mml:math> , smaller, roughly by a factor 2, than for neutrons, and a phase generally close to 12–16 h local time. No sensible differences were observed in the anisotropy parameters between solar nights and days in the polar region. The possible contribution of a second harmonic in the observed diurnal trend was also investigated.

The European Physical Journal CVol. 86(6)
University of Siena (IT), University of Pisa (IT), University of Salerno (IT), University of Salento (IT), University of Cagliari (IT), Politecnico di Torino (IT), OsloMet – Oslo Metropolitan University (NO), University of Oslo (NO), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso (IT), University of Catania (IT), Osservatorio astronomico di Bologna (IT), Istituto Nazionale di Fisica Nucleare, Centro Nazionale Analisi Fotogrammi (IT), Nello Carrara Institute of Applied Physics (IT), Istituto Nazionale di Fisica Nucleare, Trento Institute for Fundamental Physics And Applications (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Lecce (IT), Azienda Ospedaliera di Cosenza (IT), Centro Ricerche Enrico Fermi (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Bari (IT), National Interuniversity Consortium for the Physical Sciences of Matter (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Catania (IT), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Genova (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari (IT), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati (IT), World Education (US), Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (IT), Gran Sasso Science Institute (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Cosenza, University of Calabria (IT), European Organization for Nuclear Research (CH), Polytechnic University of Bari (IT), University of Genoa (IT), University of Bologna (IT), Politecnico di Milano (IT)
Consiglio Nazionale delle Ricerche, Istituto Nazionale di Fisica Nucleare
Affordable and clean energy
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Astrophysics and Cosmic Phenomena
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