A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory

Abstract

a b s t r a c tThe air fluorescence detector of the Pierre Auger Observatory is designed to perform calorimetric measurements of extensive air showers created by cosmic rays of above 10 18 eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group of monitoring instruments to record atmospheric conditions across the detector site, an area exceeding 3000 km 2 . The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements on air shower reconstructions. Between 10 18 and 10 20 eV, the systematic uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm À2to 8 g cm À2 in measurements of the shower maximum.

Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

“…By contrast, the mean free path for helium is much shorter than iron, such the composition arriving at Earth is expected to be dominated by heavy nuclei at the highest energies. As already mentioned, the highest energy UHECRs do appear to be heavier than protons (Abraham et al 2010), although the precise composition is model-and calibration-dependent and hence remains uncertain.…”

“…show that this is sufficient to produce the observed gamma-ray emission and to accelerate nuclei within the jet to ultra-high energies ∼ > 10 19 eV per particle. GRBs associated with magnetar birth therefore provides a natural explanation for the otherwise puzzling observation by the Pierre Auger Observatory that the highest energies UHECRs are composed of heavy nuclei instead of protons (Abraham et al 2010, see however Abbasi et al 2005). This model is also consistent with constraints on the non-detection of high energy neutrinos coincident with GRBs with IceCube (Abbasi et al 2011), since nuclei typically lose energy through other processes than photo-pion production, and hence are not expected to be accompanied by a neutrino flux as large as that predicted for proton-dominated compositions.…”

Constraints on the origin of ultra-high-energy cosmic rays from cosmogenic neutrinos and photons

“…Their origin still remains unknown after decades of experimental efforts. Recent experiments such as the High Resolution fly's eye (HiRes, Abbasi et al 2004), the Akeno Giant Air Shower Array (AGASA, Nagano et al 1992) and primarily the Pierre Auger Observatory (Abraham et al 2004) have increased the available cosmic ray statistics above 10 18 eV, allowing the first solid studies from the point of view of the spectrum, the composition and the arrival directions of ultra-high-energy cosmic rays (UHECRs). A sharp decrease of the UHECR flux above 3−4 × 10 19 eV possibly related to the theoretically expected GZK cut-off (Greisen 1966;Zatsepin & Kuzmin 1966) seems to be firmly established, whereas the interpretation of composition or arrival direction data as well as the consistency of the results reported by the different experiments are matters of intense debates.…”

“…We discuss the constraints brought by the Fermi measurements of the diffuse extragalactic background on the expectations for cosmogenic neutrinos or UHE photons detection. Furthermore, we discuss the possible neutrino or photon signatures from UHECR proton accelerators either in the local universe or at cosmological distances (diffuse or point sources) even if the UHECR composition becomes heavier, which is one of the plausible interpretations of the recent measurement of the longitudinal development of air showers (hereafter X max measurements) of the Pierre Auger Observatory (Abraham et al 2010a). In the next section, we briefly introduce our code that simulates the propagation of UHECR protons and nuclei and our Monte Carlo tool for the development of intergalactic electromagnetic cascades.…”

Identifying clouds over the Pierre Auger Observatory using infrared satellite data

“…The Auger Observatory thus routinely employs a number of instruments [6]: the Central Laser Facility (CLF) [7], the eXtended Laser Facility (XLF), LIDARs [8], and IR cameras, to identify clouds over the array. For most cosmic ray studies, the present system is more than adequate [9]. But information from a satellite can complete and enrich the ground measurements.…”