{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,7]],"date-time":"2026-03-07T18:00:20Z","timestamp":1772906420873,"version":"3.50.1"},"reference-count":15,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2022,3,1]],"date-time":"2022-03-01T00:00:00Z","timestamp":1646092800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>The Cosmic Ray Extremely Distributed Observatory (CREDO) pursues a global research strategy dedicated to the search for correlated cosmic rays, so-called Cosmic Ray Ensembles (CRE). Its general approach to CRE detection does not involve any a priori considerations, and its search strategy encompasses both spatial and temporal correlations, on different scales. Here we search for time clustering of the cosmic ray events collected with a small sea-level extensive air shower array at the University of Adelaide. The array consists of seven one-square-metre scintillators enclosing an area of 10 m \u00d7 19 m. It has a threshold energy ~0.1 PeV, and records cosmic ray showers at a rate of ~6 mHz. We have examined event arrival times over a period of over 2.5 years in two equipment configurations (without and with GPS timing), recording ~300 k events and ~100 k events. We determined the event time spacing distributions between individual events and the distributions of time periods which contained specific numbers of multiple events. We find that the overall time distributions are as expected for random events. The distribution which was chosen a priori for particular study was for time periods covering five events (four spacings). Overall, these distributions fit closely with expectation, but there are two outliers of short burst periods in data for each configuration. One of these outliers contains eight events within 48 s. The physical characteristics of the array will be discussed together with the analysis procedure, including a comparison between the observed time distributions and expectation based on randomly arriving events.<\/jats:p>","DOI":"10.3390\/sym14030501","type":"journal-article","created":{"date-parts":[[2022,3,1]],"date-time":"2022-03-01T21:31:47Z","timestamp":1646170307000},"page":"501","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["A Search for Cosmic Ray Bursts at 0.1 PeV with a Small Air Shower Array"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9040-9648","authenticated-orcid":false,"given":"Roger","family":"Clay","sequence":"first","affiliation":[{"name":"School of Physical Sciences, University of Adelaide, North Terrace, Adelaide 5005, Australia"}]},{"given":"Jassimar","family":"Singh","sequence":"additional","affiliation":[{"name":"School of Physical Sciences, University of Adelaide, North Terrace, Adelaide 5005, Australia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1956-9948","authenticated-orcid":false,"given":"Piotr","family":"Homola","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"given":"Olaf","family":"Bar","sequence":"additional","affiliation":[{"name":"Institute of Computer Science, Pedagogical University of Krakow, 30-084 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4828-8659","authenticated-orcid":false,"given":"Dmitry","family":"Beznosko","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Physics, Clayton State University, Morrow, GA 30260, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3023-9517","authenticated-orcid":false,"given":"Apoorva","family":"Bhatt","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"given":"Gopal","family":"Bhatta","sequence":"additional","affiliation":[{"name":"Astronomical Observatory, Jagiellonian University, 30-244 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6117-4894","authenticated-orcid":false,"given":"\u0141ukasz","family":"Bibrzycki","sequence":"additional","affiliation":[{"name":"Institute of Computer Science, Pedagogical University of Krakow, 30-084 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2104-6687","authenticated-orcid":false,"given":"Nikolay","family":"Budnev","sequence":"additional","affiliation":[{"name":"Faculty of Physics, Irkutsk State University, 664003 Irkutsk, Russia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1874-8116","authenticated-orcid":false,"given":"David E.","family":"Alvarez-Castillo","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"},{"name":"Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russia"}]},{"given":"Niraj","family":"Dhital","sequence":"additional","affiliation":[{"name":"Central Department of Physics, Tribhuvan University, Kirtipur 44613, Nepal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9636-1809","authenticated-orcid":false,"given":"Alan R.","family":"Duffy","sequence":"additional","affiliation":[{"name":"Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Melbourne 3122, Australia"}]},{"given":"Micha\u0142","family":"Frontczak","sequence":"additional","affiliation":[{"name":"Institute of Computer Science, Pedagogical University of Krakow, 30-084 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4853-5974","authenticated-orcid":false,"given":"Dariusz","family":"G\u00f3ra","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9331-4388","authenticated-orcid":false,"given":"Alok C.","family":"Gupta","sequence":"additional","affiliation":[{"name":"Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263001, India"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3977-6514","authenticated-orcid":false,"given":"Bartosz","family":"\u0141ozowski","sequence":"additional","affiliation":[{"name":"Faculty of Natural Sciences, University of Silesia in Katowice, Bankowa 9, 40-007 Katowice, Poland"}]},{"given":"Mikhail V.","family":"Medvedev","sequence":"additional","affiliation":[{"name":"Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA"},{"name":"Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA"}]},{"given":"Justyna","family":"M\u0119drala","sequence":"additional","affiliation":[{"name":"Department of Biocybernetics and Biomedical Engineering, AGH University of Science and Technology, 30-059 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7226-1750","authenticated-orcid":false,"given":"Justyna","family":"Miszczyk","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2830-9133","authenticated-orcid":false,"given":"Micha\u0142","family":"Nied\u017awiecki","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Faculty of Computer Science and Telecommunications, Cracow University of Technology, 31-155 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3699-9955","authenticated-orcid":false,"given":"Marcin","family":"Piekarczyk","sequence":"additional","affiliation":[{"name":"Institute of Computer Science, Pedagogical University of Krakow, 30-084 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6834-2344","authenticated-orcid":false,"given":"Krzysztof","family":"Rzecki","sequence":"additional","affiliation":[{"name":"Department of Biocybernetics and Biomedical Engineering, AGH University of Science and Technology, 30-059 Krakow, Poland"}]},{"given":"Jilberto","family":"Zamora-Saa","sequence":"additional","affiliation":[{"name":"Departamento de Ciencias Fisicas, Universidad Andres Bello, Piso 7, Sazie, Santiago 2212, Chile"}]},{"given":"Katarzyna","family":"Smelcerz","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Faculty of Computer Science and Telecommunications, Cracow University of Technology, 31-155 Krakow, Poland"}]},{"given":"Karel","family":"Smolek","sequence":"additional","affiliation":[{"name":"Institute of Experimental and Applied Physics, Czech Technical University in Prague, Husova 240\/5, 110 00 Prague, Czech Republic"}]},{"given":"Tomasz","family":"So\u015bnicki","sequence":"additional","affiliation":[{"name":"Department of Biocybernetics and Biomedical Engineering, AGH University of Science and Technology, 30-059 Krakow, Poland"}]},{"given":"Jaroslaw","family":"Stasielak","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5490-0835","authenticated-orcid":false,"given":"S\u0142awomir","family":"Stuglik","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7848-4207","authenticated-orcid":false,"given":"Oleksandr","family":"Sushchov","sequence":"additional","affiliation":[{"name":"Institute of Nuclear Physics Polish Academy of Sciences, 31-342 Krakow, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5845-5487","authenticated-orcid":false,"given":"Arman","family":"Tursunov","sequence":"additional","affiliation":[{"name":"Research Centre for Theoretical Physics and Astrophysics, Institute of Physics, Silesian University in Opava, Bezru\u010dovo n\u00e1m. 13, CZ-74601 Opava, Czech Republic"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2078-0580","authenticated-orcid":false,"given":"Tadeusz","family":"Wibig","sequence":"additional","affiliation":[{"name":"Theoretical Physics Department, University of Lodz, Pomorska Street 149\/153, 90-236 Lodz, Poland"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Homola, P., Beznosko, D., Bhatta, G., Bibrzycki, \u0141., Borczy\u0144ska, M., Bratek, \u0141., Budnev, N., Burakowski, D., Alvarez-Castillo, D., and Cheminant, K.A. 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