The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

Abstract

We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^{\circ }$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.

20 pages, 14 figures

References in corpus (3)

• Trigger and Aperture of the Surface Detector Array of the Pierre Auger Observatory
• Calibration of the Surface Array of the Pierre Auger Observatory
• Estimates of multipolar coefficients to search for cosmic ray anisotropies with non-uniform or partial sky coverage

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• Searches for Large-Scale Anisotropy in the Arrival Directions of Cosmic Rays Detected above Energy of $10^{19}$ eV at the Pierre Auger Observatory and the Telescope Array
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• A proposed method for measurement of cosmic-ray chemical composition based on geomagnetic spectroscopy
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• Large-Scale Distribution of Arrival Directions of Cosmic Rays Detected at the Pierre Auger Observatory Above $10$PeV