Auger Radio - Public Information

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Pierre Auger Observatory

• In the coming decades, benchmarking cosmic-ray physics at Ultra-High Energy (UHE; i.e. beyond 10¹⁸ eV) will be done at the Auger observatories in Argentina and Colorado. The ultimate goal of the Auger collaboration will be to identify the very origin of UHE cosmic rays and to unravel the mystery of the physics behind the cosmic acceleration mechanisms, leading to events in the Earth’s atmosphere with energies far beyond those achieved at any human-made accelerator. To achieve this goal, not only a precise energy measurement, but also a high angular resolution and the capability to determine the composition of rays (gamma-rays, neutrinos or leptons, and hadrons) are of paramount importance. Because of the relatively small fluxes at the highest energies, sites with an area of several thousands km² and detector systems with a high uptime are needed.

Brief History

• Initial data obtained in the 1960's by amongst others Jelley et al and Allan et al showed that the detection of radio signals, induced by cosmic rays penetrating the Earth’s atmosphere, could be a valuable observational tool for cosmic-ray studies. However, the frequency interval, where the strength of radio emission from extensive air showers peaks, is difficult to study. The reason for this difficulty lies in the emission mechanism leading to relatively strong signals below 100 MHz. In this very same region not only the galactic noise increases rapidly, but also atmospheric and human-made disturbances may lead to substantial background levels. However, in recent years new observational techniques have been developed and the available computational power, also near the front end of radio receiver systems, has revived the field. Recently, the LOPES and CODALEMA collaborations have confirmed that radio-detection techniques can be used to observe extensive air showers induced by CR’s. The LOPES collaboration observed a correlation between ground-level muon signals and radio signals. Initial calculations which are promising with respect to the strength distribution of the signal and which hint to parameters of the radio signals, which can be used for the determination of the composition, are reaching a new stage, involving state-of-the-art Monte-Carlo techniques and physics input.

Our Ambition

• The CR radio detection technique at Auger can enhance the duty cycle for the detection of UHECR’s by at least two separate detector systems (in particular radio and SD) by a factor of 10. In addition, the technique may provide information which is complementary to that from SD and FD, as it determines directly the evolution of the electromagnetic properties of the shower in the atmosphere. This complementary information might open the possibility to study the composition of the primary event. The high duty cycle will provide us with many more events which are needed for a statistical analysis to determine possible anisotropies, to identify point sources, and to get a better insight into the composition of these UHECR’s. Especially in the energy window beyond 10¹⁹ eV, where (extra-)galactic magnetic fields are thought to have little influence on the trajectory of the CR’s, radio with its high duty cycle and high pointing accuracy, could be an enormous asset for UHECR studies of Auger and opens the window to charged-particle astronomy.

• Picture above left: The Active Galactic Nucleus AGN M87 as seen in the optical window with the Hubble Space Telescope, courtesy NASA. The core is displayed as the bright dot and a jet of material is seen to protruding towards to the lower right corner. Right: Large-scale structures outside our Galaxy overlayed with the Galaxy itself, courtesy Thomas Jarrett (IPAC/Caltech). The colors is this picture are false and are an indicating from the distance of a Galaxy to Earth (red-shift); blue is close, red is far. One thinks that some of the UHECR's originate from extra-Galactic sources (as AGN's), which can be embedded in the cosmic web of the large-scale structures of the Universe.

Who we are and career options

• The people (scientists, technicians, and students) working on this project are from many countries around the world, bringing together various techniques (HF-design, electronics, computing, data-analysis) and astroparticle physics knowlegde together. Many of us will remain in this work for the following years, some will change position towards other fields once their sub-project or task is done.

• . Therefore, if you want, you can check whether there are open_positions in our institutions for this work.

Required R&D

• However, before radio detection of UHECR’s can be regarded as a mature technique, comparable in its results to those obtained from SD, FD, and hybrids, a substantial R&D program is required. This program will not only address the physics issues, but also the technological ones, and the investments and running costs. This program extends on the continued efforts performed at the LOPES and CODALEMA sites in Europe, and the before mentioned theoretical efforts describing the development of EAS’s in the Earth’s atmosphere. This program starts in 2006 and will merge with the foreseen infill detector array in Auger South. Starting in 2007, and for a period of 4 years we foresee the operation of a 20 km² engineering array at the Auger South location, which will serve as a test bed to address these engineering and physics questions leading to the design of a many thousand squared kilometer array in conjunction with Auger.
  

• In the picture above some of the prototypes are displayed, while they are being tested at the southern site of the observatory.