The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.Comision Nacional de Energia Atomica, ArgentinaFundacion AntorchasGobierno De La Provincia de Mendoza, Municipalidad de Malargue, ArgentinaNDM HoldingsValle Las Lenas, ArgentinaAustralian Research Council (ARC)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Financiadora de Estudos e Projetos (FINEP)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Ministério da Ciência, Tecnologia e Inovação do Brasil (MCTI)Academy of Sciences of the Czech Republic (AVCR) [AV0Z10100502] [AV0Z10100522] [GAAV KJB300100801] [KJB100100904] [MSMT-CR LA08016] [LC527] [1M06002] [MSM0021620859]Centre National de la Recherche Scientifique (CNRS), Centre de Calcul IN2P3/CNRSConseil Regional Ile-de-France, Departement Physique Nucleaire et Corpusculaire [PNC-IN2P3/CNRS]Departement Sciences de l`Univers (SDU-INSU/CNRS), FranceBundesministerium fur Bildung und Forschung (BMBF)Deutsche Forschungsgemeinschaft (DFG)Finanzministerium Baden-WurttembergHelmholtz-Gemeinschaft Deutscher Forschungszentren (HGF)Ministerium fur Wissenschaft und Forschung, Nordrhein-Westfalen, GermanyMinisterium fur Wissenschaft, Forschung und Kunst, Baden-Wurttemberg, GermanyIstituto Nazionale di Fisica Nucleare (INFN)Istituto Nazionale di Astrofisica (INAF)Ministero dell Istruzione, dell Universita e della Ricerca (MIUR), ItalyConsejo Nacional de Ciencia y Tecnologia (CONACYT), MexicoMinisterie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)Stichting voor Fundamenteel Onderzoek der Materie (FOM), NetherlandsMinistry of Science and Higher Education, Poland [1 P03 D 014 30] [N N202 207238]Fundacao para a Ciencia e a Tecnologia (FCT), PortugalMinistry for Higher Education, Science, and Technology, Slovenian Research Agency, SloveniaComunidad de Madrid, SpainConsejeria de Educacion de la Comunidad de Castilla La ManchaFondo Europeo de Desarrollo Regional (FEDER)Ministerio de Ciencia e Innovacion, Consolider-Ingenio, SpainGeneralitat ValencianaJunta de AndaluciaXunta de Galicia, SpainScience and Technology Facilities Council, United KingdomU.S. Department of Energy (DOE) [DE-AC02-07CH11359] [DE-FR02-04ER41300]National Science Foundation (NSF) [0450696]Grainger Foundation USAALFA-EC / HELENEuropean Union [MEIF-CT-2005-025057] [PIEF-GA-2008-220240]United Nations Educational, Scientific and Cultural Organization (UNESCO

Description of atmospheric conditions at the Pierre auger observatory using the global data assimilation system (GDAS)

Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malargüe and averaged monthly models, the utility of the GDAS data is shown. </p

Ultrahigh energy neutrinos at the Pierre Auger observatory

The observation of ultrahigh energy neutrinos (UHEνs) has become a priority in experimental astroparticle physics. UHEνs can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going ν) or in the Earth crust (Earth-skimming ν), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHEνs in the data collected with the ground array of the Pierre Auger Observatory. This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHEνs in the EeV range and above

The rapid atmospheric monitoring system of the Pierre Auger Observatory

The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 1017 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or "rapid") monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction. </p

Large-scale distribution of arrival directions of cosmic rays detected above 10¹⁸ eV at the Pierre Auger observatory

A thorough search for large-scale anisotropies in the distribution of arrival directions of cosmic rays detected above 1018 eV at the Pierre Auger Observatory is presented. This search is performed as a function of both declination and right ascension in several energy ranges above 1018 eV, and reported in terms of dipolar and quadrupolar coefficients. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Assuming that any cosmic-ray anisotropy is dominated by dipole and quadrupole moments in this energy range, upper limits on their amplitudes are derived. These upper limits allow us to test the origin of cosmic rays above 1018 eV from stationary Galactic sources densely distributed in the Galactic disk and predominantly emitting light particles in all directions.</p