Progress in air shower radio measurements: Detection of distant events

Fachbereich Physik, Universität Siegen, 57072 Siegen, Germany
Astroparticle Physics (Impact Factor: 3.58). 11/2006; 26(4-5):332-340. DOI: 10.1016/j.astropartphys.2006.07.003
Source: arXiv


Data taken during half a year of operation of 10 LOPES antennas (LOPES-10), triggered by EAS observed with KASCADE-Grande have been analysed. We report about the analysis of correlations of radio signals measured by LOPES-10 with extensive air shower events reconstructed by KASCADE-Grande, including shower cores at large distances. The efficiency of detecting radio signals induced by air showers up to distances of 700 m from the shower axis has been investigated. The results are discussed with special emphasis on the effects of the reconstruction accuracy for shower core and arrival direction on the coherence of the measured radio signal. In addition, the correlations of the radio pulse amplitude with the primary cosmic ray energy and with the lateral distance from the shower core are studied.

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    • "4 Jun 2014 ns between rising edges of the clock. The widths of the radio pulses ∼100 ns are consistent with the theoretical estimations [3], [4] and the LOPES data [5], [6]. The width of ∼100 ns by the 200 MSps sampling corresponds to 20 time bins. "
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    ABSTRACT: Experiments that observe coherent radio emission from extensive air showers induced by ultra-high energy cosmic rays are designed for a detailed study of the development of the electromagnetic part of air showers. Radio detectors can operate with 100% up time as e.g. surface detectors based on water-Cherenkov tanks. They are being developed for ground-based experiments (e.g. the Pierre Auger Observatory) as another type of air shower detector in addition to the fluorescence detectors, which operate with only ~10% of duty in dark nights. The radio signals from air showers are caused by the coherent emission due to geomagnetic radiation and charge excess processes. Currently used self-triggers in radio detectors often generate a dense stream of data, which is analyzed afterwards. Huge amounts of registered data requires a significant man-power for the off-line analysis. An improvement of the trigger efficiency becomes a relevant factor. In this work, Morlet wavelets with various scaling factors were used for an analysis of real data from the Auger Engineering Radio Array and for an optimization of the utilization of the resources in an FPGA. The wavelet analysis showed that the power of events is concentrated mostly in a limited range of the frequency spectrum (consistent with a range imposed by the input analog band-pass filter). However, we found several events with suspicious spectral characteristics, where the signal power is spread over the full band-width sampled by a 200 MHz digitizer with significant contribution of very high and very low frequencies. These events may not origin from cosmic ray showers but can be human-made contaminations. The engine of the wavelet analysis can be implemented into the modern powerful FPGA and can remove suspicious events on-line to reduce the trigger rate.
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    ABSTRACT: We present simulations performed with REAS2, a new Monte Carlo code for the calculation of geosynchrotron radio emission from extensive air showers. The code uses thoroughly tested time-domain radio emission routines in conjunction with a realistic air shower model based on per-shower multi-dimensional CORSIKA-generated histograms. We assess in detail how the transition from simpler, parametrised, to realistic, CORSIKA-based particle distributions affects the predicted radio emission from a typical 1017 eV air shower. The effects of eliminating a previously needed free parameter and adopting realistic electron to positron ratios are also discussed. Compared with earlier calculations based on parametrised showers, REAS2 simulations predict slightly weaker and in some cases narrower pulses. In addition, a pronounced east–west versus north–south asymmetry arises in the emission pattern, and the radio pulses become generally unipolar. Finally, we demonstrate how REAS2 can be used to study radio pulse shapes and their relation to shower characteristics such as the longitudinal air shower development.
    Astroparticle Physics 06/2007; 27(5-27):392-405. DOI:10.1016/j.astropartphys.2007.01.006 · 3.58 Impact Factor
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