Krijn D. de Vries

A realistic treatment of geomagnetic Cherenkov radiation from cosmic ray air showers

We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic field. We discuss the importance of a correct treatment of the index of refraction in air, given by the law of Gladstone and Dale, which affects the pulses enormously for certain configurations, compared to a simplified treatment using a constant index. We predict in particular a geomagnetic Cherenkov radiation, which provides strong signals at high frequencies (GHz), for certain geometries together with “normal radiation” from the shower maximum, leading to a double peak structure in the frequency spectrum. We also provide some information about the numerical procedures referred to as EVA 1.0.

The air shower maximum probed by Cherenkov effects from radio emission

Radio detection of cosmic-ray-induced air showers has come to a ight the last decade. Along with the experimental eorts, several theoretical models were developed. The main radio-emission mechanisms are established to be the geomagnetic emission due to deection of electrons and positrons in Earth’s magnetic eld and the charge-excess emission due to a net electron excess in the air shower front. It was only recently shown that Cherenkov eects play an important role in the radio emission from air showers. In this article we show the importance of these eects to extract quantitatively the position of the shower maximum from the radio signal, which is a sensitive measure for the mass of the initial cosmic ray. We also show that the relative magnitude of the charge-excess and geomagnetic emission changes considerably at small observer distances where Cherenkov eects apply.

The Giant Radio Array for Neutrino Detection

The Giant Radio Array for Neutrino Detection (GRAND) is a planned array of ~ 2·105 radio antennas deployed over ~ 200 000 km2 in a mountainous site. It aims primarly at detecting high-energy neutrinos via the observation of extensive air showers induced by the decay in the atmosphere of taus produced by the interaction of cosmic neutrinos under the Earth surface. GRAND aims at reaching a neutrino sensitivity of 5 · 10−11 E −2 GeV−1 cm−2 s−1 sr−1 above 3 · 1016 eV. This ensures the detection of cosmogenic neutrinos in the most pessimistic source models, and ~50 events per year are expected for the standard models. The instrument will also detect UHECRs and possibly FRBs. Here we show how our preliminary design should enable us to reach our sensitivity goals, and discuss the steps to be taken to achieve GRAND, while the compelling science case for GRAND is discussed in more details in [1].

The cosmic-ray air-shower signal in Askaryan radio detectors

We discuss the radio emission from high-energy cosmic-ray induced air showers hitting Earths surface before the cascade has died out in the atmosphere. The induced emission gives rise to a radio signal which should be detectable in the currently operating Askaryan radio detectors built to search for the GZK neutrino flux in ice. The in-air emission, the in-ice emission, as well as a new component, the coherent transition radiation when the particle bunch crosses the air-ice boundary, are included in the calculations.

Coherent radiation from extensive air showers

The generic properties of the emission of coherent radiation from a moving charge distribution are discussed. The general structure of the charge and current distributions in an extensive air shower are derived. These are subsequently used to develop a very intuitive picture for the properties of the emitted radio pulse. Using this picture can be seen that the structure of the pulse is a direct reflection of the shower profile. At higher frequencies the emission is suppressed because the wavelength is shorter than the important length scale in the shower. It is shown that radio emission can be used to distinguish proton and iron induced air showers.

Analytic Calculation of Radio Emission from Extensive Air Showers subjected to Atmospheric Electric Fields

We have developed a code that semi-analytically calculates the radio footprint (intensity and polarization) of an extensive air shower subject to atmospheric electric fields. This can be used to reconstruct the height dependence of atmospheric electric field from the measured radio footprint. The various parameterizations of the spatial extent of the induced currents are based on the results of Monte-Carlo shower simulations. The calculated radio footprints agree well with microscopic CoREAS simulations.

The EVA code: Macroscopic modeling of radio emission from air showers based on full MC simulations including a realistic index of refraction

A comprehensive overview of the newly developed EVA-code is given. To take into account Cherenkov effects and include realistic showers in combination with shower-to-shower fluctuations we have developed the EVA code (Electric fields, using a Variable index of refraction in Air shower simulations code). The EVA-code is based on histograms obtained from a full Monte-Carlo CONEX simulation to calculate radio emission from cosmic-ray-induced air showers. The EVA-code makes use of the finite dimensions of the particle distributions to overcome the divergences in the fields due to Cherenkov effects without making any approximations.

Probing the radar scattering cross-section for high-energy particle cascades in ice

Recently the radar scattering technique to probe neutrino induced particle cascades above PeV energies in ice was investigated. The feasibility of the radar detection method was shown to crucially depend on several up to now unknown plasma properties, such as the plasma lifetime and the free charge collision rate. To determine these parameters, a radar scattering experiment was performed at the Telescope Array Electron Light Source facility, where a beam of high-energy electrons was directed in a block of ice. The induced ionization plasma was consequently probed using a radar detection set-up detecting over a wide frequency range from 200 MHz up to 2 GHz. First qualitative results of this experiment will be presented.

The Giant Radio Array for Neutrino Detection (GRAND) : Present and Perspectives

The Giant Radio Array for Neutrino Detection (GRAND) aims at detecting ultra-high energy extraterrestrial neutrinos via the extensive air showers induced by the decay of tau leptons created in the interaction of neutrinos under the Earths surface. Consisting of an array of

The GRANDproto35 experiment

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