Results of a self-triggered prototype system for radio-detection of extensive air showers at the Pierre Auger Observatory

Abstract

We describe the experimental setup and the results of RAuger, a small radio-antenna array, consisting of three fully autonomous and self-triggered radio-detection stations, installed close to the center of the Surface Detector (SD) of the Pierre Auger Observatory in Argentina. The setup has been designed for the detection of the electric field strength of air showers initiated by ultra-high energy cosmic rays, without using an auxiliary trigger from another detection system. Installed in December 2006, RAuger was terminated in May 2010 after 65 registered coincidences with the SD. The sky map in local angular coordinates (i.e., zenith and azimuth angles) of these events reveals a strong azimuthal asymmetry which is in agreement with a mechanism dominated by a geomagnetic emission process. The correlation between the electric field and the energy of the primary cosmic ray is presented for the first time, in an energy range covering two orders of magnitude between 0.1 EeV and 10 EeV. It is demonstrated that this setup is relatively more sensitive to inclined showers, with respect to the SD. In addition to these results, which underline the potential of the radio-detection technique, important information about the general behavior of self-triggering radio-detection systems has been obtained. In particular, we will discuss radio self-triggering under varying local electric-field conditions. * Authors are listed on the following pages.

Radio Detection of Cosmic Rays: Present and Future

“…Significant effort has been made to develop a "self-triggered radio detector" and some successes have been achieved [15]. In principle, it is of course possible to trigger read-out of radio detectors on the basis of pulses measured in the radio signals themselves.…”

Probing the radio emission from air showers with polarization measurements

“…In the present analysis only data from those RDSs were selected where the difference between the relative gain for their two polarization directions was less than 5%. Furthermore, it is well known [47][48][49] that thunderstorm conditions may cause a substantial change of the radio signal strength from air showers as compared to the signal strength obtained under fair-weather conditions. The atmospheric monitoring systems of the observatory, located at the BLS and at AERA (see Fig.…”

Laboratory tests of two-dimensional wavelet trigger in radio detection of cosmic rays

“…Short but coherent radio pulses of duration from 10 ns up to several 100 ns are generated with an electric field strength increasing approximately linearly with the energy of the primary cosmic particle inducing the extended air showers (EAS), i.e. quadratic dependence of the radio pulse energy vs. primary particle energy [5]- [9]. In contrast to the fluorescence technique with a duty cycle of about 10% (fluorescence detectors can operate only during moonless nights [10]), the radio technique allows nearly fulltime measurements and long-range observations because of the high transparency of the air to radio signals in the investigated frequency range.…”