High-energy cosmic rays impinging onto the atmosphere of the Earth induce cascades of secondary particles: extensive air showers. Many of the particles in a shower are electrons and positrons. The ...electrons and positrons interact with the geomagnetic field and emit radiation. We detect such radiation at frequencies of tens to hundreds of MHz with the Auger Engineering Radio Array (AERA) at the Pierre Auger Observatory in Argentina. The objective is to investigate the properties of cosmic rays at the expected transition from Galactic to an extragalactic origin at energies around 1017 to 1018 eV. We discuss the recent progress in radio detection of ultra-high-energy cosmic rays with AERA. To this end, we elaborate on our measurements of shower properties, such as the lateral distribution of the radio emission at ground level. In addition, we present methods to reconstruct the properties of the primary particle from the radio data.
Lightning Imaging with LOFAR Scholten, Olaf; Buitink, Stijn; Dina, Roxana ...
EPJ Web of Conferences,
01/2017, Letnik:
135
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
We show that LOFAR can be used as a lightning mapping array with a resolution that is orders of magnitude better than existing arrays. In addition the polarization of the radiation can be used to ...track the direction of the stepping discharges.
The Pierre Auger Observatory, the world-largest cosmic-ray detector, has been measuring ultrahigh-energy cosmic rays in the Southern Hemisphere since 2004. A major upgrade program has begun recently, ...which will enhance the particle-identification sensitivity of the Observatory's surface detector. This upgrade program includes the replacement of the electronics boards of more than 1600 surface detector stations. A test system has been developed by the particle physics group at the University of Siegen, which allows emulating the response of a surface detector station to perform functionality verification tests of the new electronics boards. The test system consists of a single-board Linux-based computer, on which the system control and data analysis software is running, a 6-channel 500 MS/s digital-to-analogue converter card, which is equipped with a Field Programmable Gate Array and an ARM-based processor, that allow generating high-precision arbitrary pulse forms, a microcontroller data acquisition and a programmable power card, which supplies voltages for the test system and the system under test. The test system can be used for versatile applications without additional external equipment. In this paper the hardware, the software and the performance of the test system will be presented.
The Auger Engineering Radio Array (AERA) aims to detect extensive air showers caused by the interactions of ultra-high energy cosmic rays with the Earth's atmosphere, providing complementary ...information to the Auger surface, fluorescence and muon detectors. AERA, currently consisting of 124 radio stations, comprises an area of about 6 km\(^{2}\). The main objective for exploiting a radio detector is to measure the fundamental air-shower parameters, such as the direction, energy and composition. We have developed reconstruction strategies and algorithms to precisely measure the air-shower parameters with high efficiency. In addition, we will present the results obtained by applying the reconstruction strategies on the experimental data taken by AERA.
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.
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.
Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the Surface Detector array of the Pierre Auger Observatory. We report here on searches through Auger data from ...1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultra-high energy neutrinos that challenges the Waxman-Bahcall bound predictions. Neutrino identification is attempted using the broad time-structure of the signals expected in the SD stations, and is efficiently done for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for "Earth-skimming" neutrino interactions in the case of tau neutrinos. In this paper the searches for downward-going neutrinos in the zenith angle bins \(60^\circ-75^\circ\) and \(75^\circ-90^\circ\) as well as for upward-going neutrinos, are combined to give a single limit. The \(90\%\) C.L. single-flavor limit to the diffuse flux of ultra-high energy neutrinos with an \(E^{-2}\) spectrum in the energy range \(1.0 \times 10^{17}\) eV - \(2.5 \times 10^{19}\) eV is \(E_\nu^2 dN_\nu/dE_\nu < 6.4 \times 10^{-9}~ {\rm GeV~ cm^{-2}~ s^{-1}~ sr^{-1}}\).
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.
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