This paper reports on the measurement of the large-scale anisotropy in the distribution of cosmic-ray arrival directions using the data collected by the air shower detector ARGO-YBJ from 2008 January to 2009 December, during the minimum of solar activity between cycles 23 and 24. In this period, more than 2 x 10(11) showers were recorded with energies between similar to 1 and 30 TeV. The observed two-dimensional distribution of cosmic rays is characterized by two wide regions of excess and deficit, respectively, both of relative intensity similar to 10(-3) with respect to a uniform flux, superimposed on smaller size structures. The harmonic analysis shows that the large-scale cosmic-ray relative intensity as a function of R.A. can be described by the first and second terms of a Fouries series. The high event statistics allow the study of the energy dependence of the anistropy, showing that the amplitude increases with energy, with a maximum intensity at similar to 10 TeV, and then decreases while the phase slowly shifts toward lower values of R.A. with increasing energy. The ARGO-YBJ data provide accurate observations over more than a decade of energy around this feature of the anisotropy spectrum.

ARGO-YBJ OBSERVATION OF THE LARGE-SCALE COSMIC RAY ANISOTROPY DURING THE SOLAR MINIMUM BETWEEN CYCLES 23 AND 24 / Iuppa, Roberto; ARGO YBJ, Collaboration. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 809:1(2015), pp. 9001-9009. [10.1088/0004-637X/809/1/90]

ARGO-YBJ OBSERVATION OF THE LARGE-SCALE COSMIC RAY ANISOTROPY DURING THE SOLAR MINIMUM BETWEEN CYCLES 23 AND 24

Iuppa, Roberto;
2015

Abstract

This paper reports on the measurement of the large-scale anisotropy in the distribution of cosmic-ray arrival directions using the data collected by the air shower detector ARGO-YBJ from 2008 January to 2009 December, during the minimum of solar activity between cycles 23 and 24. In this period, more than 2 x 10(11) showers were recorded with energies between similar to 1 and 30 TeV. The observed two-dimensional distribution of cosmic rays is characterized by two wide regions of excess and deficit, respectively, both of relative intensity similar to 10(-3) with respect to a uniform flux, superimposed on smaller size structures. The harmonic analysis shows that the large-scale cosmic-ray relative intensity as a function of R.A. can be described by the first and second terms of a Fouries series. The high event statistics allow the study of the energy dependence of the anistropy, showing that the amplitude increases with energy, with a maximum intensity at similar to 10 TeV, and then decreases while the phase slowly shifts toward lower values of R.A. with increasing energy. The ARGO-YBJ data provide accurate observations over more than a decade of energy around this feature of the anisotropy spectrum.
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Iuppa, Roberto; ARGO YBJ, Collaboration
ARGO-YBJ OBSERVATION OF THE LARGE-SCALE COSMIC RAY ANISOTROPY DURING THE SOLAR MINIMUM BETWEEN CYCLES 23 AND 24 / Iuppa, Roberto; ARGO YBJ, Collaboration. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 809:1(2015), pp. 9001-9009. [10.1088/0004-637X/809/1/90]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/162845
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