Measurements of Inclined Air Showers with the Auger Engineering Radio Array at the Pierre Auger Observatory
2019 July 22
The Auger Engineering Radio Array (AERA) comprises 153 autonomous radio antenna stations distributed over an area of 17 km² . It is operated in coincidence with the surface detector array and fluorescence telescopes of the Pierre Auger Observatory so that hybrid observations of extensive air showers initiated by cosmic rays in the EeV energy range can be performed. A first analysis of the radio emission of more than 500 inclined air showers with zenith angles between 60° and 84° was published last year. Here, we provide an update of the analysis including recent data, approximately quadrupling the event statistics. For inclined showers, the radio signal is found to be distributed over an area of several km² , allowing air showers to be measured with radio antennas on a grid as sparse as the 1500 m spacing of the 1600 water-Cherenkov Detector (WCD) stations. For a subset of these inclined events, for which the primary energy can be reconstructed with the data from the WCD array, we verify that the measured radio amplitudes agree with Monte Carlo simulations made using CoREAS. Special challenges of a radio event reconstruction dedicated to inclined air showers will also be discussed.