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Anisotropy In Cosmic-Ray Arrival Directions In The Southern Hemisphere Based On Six Years Of Data From The Icecube Detector
Univ Adelaide, Dept Phys, Adelaide, SA 5005, Australia..
Tech Univ Munich, D-85748 Garching, Germany..
DESY, D-15735 Zeuthen, Germany..
Univ Adelaide, Dept Phys, Adelaide, SA 5005, Australia..
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 826, no 2, 220Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory accumulated a total of 318 billion cosmic-ray-induced muon events between 2009 May and 2015 May. This data set was used for a detailed analysis of the sidereal anisotropy in the arrival directions of cosmic rays in the TeV to PeV energy range. The observed global sidereal anisotropy features large regions of relative excess and deficit, with amplitudes of the order of 10(-3) up to about 100 TeV. A decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole (l <= 4) moments. However, higher multipole components are found to be statistically significant down to an angular scale of less than 10 degrees, approaching the angular resolution of the detector. Above 100 TeV, a change in the morphology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5 PeV, the highest energies currently accessible to IceCube. No time dependence of the large-and small-scale structures is observed in the period of six years covered by this analysis. The high-statistics data set reveals more details of the properties of the anisotropy and is potentially able to shed light on the various physical processes that are responsible for the complex angular structure and energy evolution.

Place, publisher, year, edition, pages
2016. Vol. 826, no 2, 220
Keyword [en]
astroparticle physics, cosmic rays
National Category
Astronomy, Astrophysics and Cosmology Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-308242DOI: 10.3847/0004-637X/826/2/220ISI: 000381977900120OAI: oai:DiVA.org:uu-308242DiVA: diva2:1049516
Funder
Swedish Research CouncilSwedish Polar Research SecretariatSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg FoundationGerman Research Foundation (DFG)Australian Research Council
Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2016-11-24Bibliographically approved

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Boersma, David J.Botner, OlgaEuler, SebastianHallgren, Allande los Heros, CarlosStröm, RickardTaavola, HenricUnger, Lisa E.
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