Radio pulses from cosmic ray air showers - Boosted Coulomb and Cherenkov fields

High-energy cosmic rays passing through the Earth's atmosphere produce extensive showers whose charges emit radio frequency pulses. Despite the low density of the Earth's atmosphere, this emission should be affected by the air refractive index because the bulk of the shower particles move roughly at the speed of radio waves, so that the retarded altitude of emission, the relativistic boost and the emission pattern are modified. We consider in this paper the contribution of the boosted Coulomb and the Cherenkov fields and calculate analytically the spectrum using a very simplified model in order to highlight the main properties. We find that typically the lower half of the shower charge energy distribution produces a boosted Coulomb field, of amplitude comparable to the levels measured and to those calculated previously for synchrotron emission. Higher energy particles produce instead a Cherenkov-like field, whose amplitude may be smaller because both the negative charge excess and the separation between charges of opposite signs are small at these energies.Comment: 10 figures - Accepted by Astronomy & Astrophysic

Characteristics of radioelectric fields from air showers induced by UHECR measured with CODALEMA

International audienceThe detection of radio transients associated with extensive air showers EAS induced by ultra high energy cosmic rays with the apparatus CODALEMA allows for the first time the characterisation and sampling of electric field features . Core location together with the electric field profile are determined on an event-by-event basis.The possibility to discriminate an EAS event using a self triggering network of antennas opens the possible deployment of complementary set-ups to existing large surface detectors in order to study the longitudinal development of EAS as well as a contribution to the energy determination and nature of UHECR

REAS3: Monte Carlo simulations of radio emission from cosmic ray air showers using an "end-point" formalism

In recent years, the freely available Monte Carlo code REAS for modelling radio emission from cosmic ray air showers has evolved to include the full complexity of air shower physics. However, it turned out that in REAS2 and all other time-domain models which calculate the radio emission by superposing the radiation of the single air shower electrons and positrons, the calculation of the emission contributions was not fully consistent. In this article, we present a revised implementation in REAS3, which incorporates the missing radio emission due to the variation of the number of charged particles during the air shower evolution using an "end-point formalism". With the inclusion of these emission contributions, the structure of the simulated radio pulses changes from unipolar to bipolar, and the azimuthal emission pattern becomes nearly symmetric. Remaining asymmetries can be explained by radio emission due to the variation of the net charge excess in air showers, which is automatically taken into account in the new implementation. REAS3 constitutes the first self-consistent time-domain implementation based on single particle emission taking the full complexity of air shower physics into account, and is freely available for all interested users.Comment: 18 pages, 13 figures accepted by Astroparticle Physics (2010

The TIANSHAN Radio Experiment for Neutrino Detection

An antenna array devoted to the autonomous radio-detection of high energy cosmic rays is being deployed on the site of the 21 cm array radio telescope in XinJiang, China. Thanks in particular to the very good electromagnetic environment of this remote experimental site, self-triggering on extensive air showers induced by cosmic rays has been achieved with a small scale prototype of the foreseen antenna array. We give here a detailed description of the detector and present the first detection of extensive air showers with this prototype.Comment: 37 pages, 15 figures. Astroparticle Physics (in press

Radio detection of cosmic rays in the Pierre Auger Observatory

In small-scale experiments such as CODALEMA and LOPES, radio detection of cosmic rays has demonstrated its potential as a technique for cosmic ray measurements up to the highest energies. Radio detection promises measurements with high duty-cycle, allows a direction reconstruction with very good angular resolution, and provides complementary information on energy and nature of the cosmic ray primaries with respect to particle detectors at ground and fluorescence telescopes. Within the Pierre Auger Observatory, we tackle the technological and scientific challenges for an application of the radio detection technique on large scales. Here, we report on the results obtained so far using the Southern Auger site and the plans for an engineering array of radio detectors covering an area of ~20 km^2.Comment: 4 pages, Proceedings of the 11th Pisa Meeting on Advanced Detector

Macroscopic Geo-Magnetic Radiation Model; Polarization effects and finite volume calculations

An ultra-high-energy cosmic ray (UHECR) colliding with the Earth's atmosphere gives rise to an Extensive Air Shower (EAS). Due to different charge separation mechanisms within the thin shower front coherent electromagnetic radiation will be emitted within the radio frequency range. A small deviation of the index of refraction from unity will give rise to Cherenkov radiation up to distances of 100 meters from the shower core and therefore has to be included in a complete description of the radio emission from an EAS. Interference between the different radiation mechanisms, in combination with different polarization behavior will reflect in a lateral distribution function (LDF) depending on the orientation of the observer and a non-trivial fall-off of the radio signal as function of distance to the shower core.Comment: Proceedings of the ARENA2010 conference, Nantes, Franc

Development of a radio-detection method array for the observation of ultra-high energy neutrino induced showers

The recent demonstration by the CODALEMA Collaboration of the ability of the radio-detection technique for the characterization of UHE cosmic-rays calls for the use of this powerful method for the observation of UHE neutrinos. For this purpose, an adaptation of the existing 21CM Array (China) is presently under achievment. In an exceptionally low electromagnetic noise level, 10160 log-periodic 50-200 MHz antennas sit along two high valleys, surrounded by mountain chains. This lay-out results in 30-60 km effective rock thicnesses for neutrino interactions with low incidence trajectories along the direction of two 4-6 km baselines. We will present first in-situ radio measurements demonstrating that this environment shows particularly favourable conditions for the observation of electromagnetic decay signals of taus originating from the interaction of 10^17-20 eV tau neutrinos.Comment: 4pages, 3 figures, Contribution to appear in the proceedings of ARENA 2008 conferenc

Limonest – Zac des Bruyères (tranche 2)

hydraulique, aqueduc, canal, fosse, industrie lithique, céramique Une fouille préventive a été réalisée en mai 2014 sur l’emplacement d’un tronçon de l’aqueduc antique de la Brévenne à l’ouest de la commune de Limonest, en limite avec la commune de Dardilly. Cet aqueduc est l’un des quatre mis en place pour alimenter en eau Lugdunum. Il prélevait les eaux de sources du Plateau lyonnais sur la rive gauche de la rivière d’Orjolle à proximité de la Brévenne, à 630 m d’altitude. Il les acheminait..

Lyon (2e) – Reconversion du site de l’Hôtel Dieu (tranches 7 et 8), 1 place de l’Hôpital

Trois sondages préalables à la réalisation d’une galerie technique ont été réalisés dans et en bordure de la grande galerie de l’Hôtel Dieu, dans le cadre de la réhabilitation de cet ancien hôpital fondé à la période médiévale et désaffecté en 2010. Le premier sondage s’est avéré négatif. Le deuxième, localisé au pied des fondations orientales du grand dôme, dans l’ancienne Cour de la Cuisine, a permis de mettre au jour un mur appareillé du xviiie s. associé à une voirie, correspondant probab..