Mass composition of ultra-high energy cosmic rays : a study based on elongation rate of depth of shower maximum measured at the Pierre Auger Observatory

An analysis of the mass composition of UHECRs based on the Xmax elongation rate (ER) within the energy range 10^{17.8} -10^{20.0} eV is performed, using Xmax data collected by the Pierre Auger Observatory from December 2004 to December 2012. The development of ER with energy is investigated by estimating the ER and the rate of change of ER with energy in sliding windows. In order to make it easier to observe the effect of a change in the proton fraction on the overall primary cosmic ray composition, the data has been truncated into "light" and "heavy" components based on a cut on the Xmax value above which 50% of helium showers produced with EPOS-LHC survive. The "light" component should be dominated by proton and helium nuclei. The behavior of the ER of the "light" part potentially allows one to distinguish changes in the mass composition from changes in the properties of hadronic interactions. The rate of change of ER with energy is observed to be negative and differs from zero for lg(E/eV) approx 18.2-18.5 by approx 3 sigma: primary mass is increasing and the rate of change of primary mass might not be constant. The increase in primary mass might be mostly due to a reduction of the fraction of protons. The "heavy" subset seems to be consistent with a constant primary mass. An interpretation of the data as being due to a pure proton composition with an unexpectedly large increase in interaction cross-section might be in tension with the behavior of ER of the "light" component.Es wird eine Analyse der Massenzusammensetzung der ultrahochenergetischen kosmischen Strahlung vorgestellt, die auf der Xmax-Elongationsrate (ER) im Energiebereich 10^{17.8} - 10^{20.0} eV basiert und Daten des Pierre-Auger-Observatoriums verwendet, die zwischen Dezember 2004 und Dezember 2012 aufgenommen wurden. Die Entwicklung der ER mit der Energie wird untersucht, indem die ER und die Änderungsrate der ER mit der Energie in kleinen Energiebins bestimmt wird. Um die Beobachtung des Effekts einer Änderung im Anteil von Protonen an der gesamten primären Massenzusammensetzung zu erleichtern, wurden die Daten in eine "leichte" und eine "schwere" Komponente eingeteilt mit Hilfe eines Schnitts auf Xmax, der so definiert ist, dass 50% der mit EPOS-LHC simulierten Helium-Luftschauer überleben. Die "leichte" Komponente sollte durch Protonen und Helium-Kerne dominiert sein. Die Untersuchung der ER der "leichten" Komponente ermöglicht es, Änderungen der Massenzusammensetzung und Änderungen in den Eigenschaften der hadronischen Wechselwirkungen zu unterscheiden. Die berechnete Änderungsrate der ER mit der Energie ist negativ und verschieden von Null für lg(E/eV) approx 18.2-18.5 mit einer Signifikanz von approx 3 sigma: Die primäre Masse steigt und es gibt Hinweise auf eine nicht konstante Änderungsrate der primaren Masse. Der Anstieg der primären Masse kann vorwiegend aus einer Verringerung des Protonanteils resultieren. Die "schwere" Komponente scheint verträglich mit einer konstanten primären Masse zu sein. Eine Interpretation der Daten als reine Proton-Zusammensetzung mit einem unerwartet starken Anstieg des Wechselwirkungsquerschnitts scheint im Widerspruch zu stehen zum beobachtenen Verhalten der "leichten" Komponente

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

The Power of the “Audience-Public”: Interactive Radio in Africa

The convergence of newer digital communication technologies with more established radio and television broadcasts is shifting opportunities for news media to impact upon citizen-state relations. These nascent possibilities are pronounced on the African continent, where mobile telephony and increasingly plural media landscapes have given rise to popular and widespread interactive talk shows. The involvement of audience voices alters the nature of the media space where political communication happens. This paper focuses on how and why interactive broadcast media intervene into relations between citizens and authorities in new and powerful ways. Through a comparative study of interactive shows in Zambia and Kenya, this paper interrogates what audience participation means for the political nature and possibilities of the interactive radio and TV broadcast. In so doing, it shows how the indeterminate audience is the basis for competing imaginaries about power, authority and belonging among the different participants in the show, including politicians, media professionals and audience members. The political significance of the ‘audience-public’, brought into being through the interactive broadcast, it is argued, lies in the very fact that multiple and competing imaginaries are at play, which are invested in by actors pursuing diverse ends and thereby have tangible political effects.The research for this article was jointly funded by the UK Economic and Social Research Council (ESRC) and Department for International Development (DFID) (ES/J018945/1) as part of the ‘Politics and Interactive Media in Africa’ (PiMA) research project

Käytännön kosteikkosuunnittelu

Maatalouden vesiensuojelua edistetään monin tavoin. Ravinteita ja eroosioainesta sisältäviä valumavesiä pyritään puhdistamaan erilaisissa kosteikoissa. Tämä opas on kirjoitettu avuksi pienimuotoisten kosteikkojen perustamiseen. Oppaassa esitetään käytännönläheisesti kosteikon toteuttamisen eri vaiheet paikan valinnasta suunnitteluun ja rakentamiseen. Vuonna 2010 julkaistun painoksen tiedot on saatettu ajantasalle. Julkaisu on toteutettu osana Tehoa maatalouden vesiensuojeluun (TEHO) -hanketta ja päivitetty TEHO Plus -hankkeen toimesta. Oppaan toivotaan lisäävän kiinnostusta kosteikkojen suunnitteluun ja edelleen niiden rakentamiseen

Erratum: Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory

We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 ⋅ 10(18) eV, i.e. the region of the all-particle spectrum above the so-called ankle feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated through a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies, hard spectra and heavy chemical composition. We also show that uncertainties about physical quantities relevant to UHECR propagation and shower development have a non-negligible impact on the fit results