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FNWI --- IMAPP Department of Astrophysics
Radboud University > Faculty of Science > Department of Astrophysics

Detecting air showers from cosmic rays with LOFAR

Group Members

Additional memembers of the LOFAR Key Science Project: Cosmic Rays

Former members

Recent Publications

  • Detecting cosmic rays with the LOFAR radio telescope, (P.Schellart et al. 2013) Astronomy & Astrophysics, 560, A98 Arxiv

Full description of data analysis framework for LOFAR cosmic rays and discussion of initial dataset.

  • Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR, (A. Nelles et al. 2014) Astroparticle Physics 2015 Arxiv

Using the high-band antennas for air shower detection. Confirming the dominant emission model and the importance of Cherenkov effects in radio detection.

  • A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles, (S. Buitink et al. 2014) Phys Rev D. Arxiv

Describing the method of determining Xmax from radio data. Radio achieves resolutions comparable to those of the currently leading techniques.

  • Polarized radio emission from cosmic ray air showers measured with LOFAR, (P. Schellart et al. 2014) JCAP Arxiv

Study of the polarization of the signal. The two emission mechanisms can be identified. Furthermore, we show that the “charge excess fraction” is a function of the zenith angle, as well as the distance to the shower axis.

  • The shape of the radio wavefront of extensive air showers as measured with LOFAR, (A. Corstanje et al. 2014) Astroparticle Physics, 60, 2014, 22-31 Arxiv

Study of the measured wavefronts. On a single event basis (and for the whole set) it can be concluded that a hyperbola describes the data best.

  • LORA: A scintillator array for LOFAR to measure extensive air showers, (S. Thoudam et al. 2014) Accepted for publication in Nuclear Instrument and Methods A

Description of the particle array LORA, including all technical details and the measurement of the energy deposition

  • A parameterization or the radio emission of air showers as predicted by CoREAS simulations and applied to LOFAR measurements, (A. Nelles et al. 2014) Astroparticle Physics, 60, 2014, 13-24 Arxiv

Development of a two-dimensional “radio LDF”. A five parameter fit describes the LOFAR data very well. The parameters show a direct sensistivity to the energy and the height of the shower maximum.

  • LOFAR: The LOw-Frequency ARray, (van Haarlem et al. 2013) Astronomy & Astrophysics, 556, A2 Arxiv

General LOFAR overview and reference article. It puts the science case of the Cosmic Ray Key Science Project into context with the other projects at LOFAR.

Background

Cosmic Rays are energetic particles, which arrive on Earth from outer space. Mainly, these particles are ionized atomic nuclei of elements from hydrogen to iron, but also electrons, positrons, photons, and neutrinos.

The incoming particles lose their energy in collisions with other particles in the atmosphere of the Earth. This results in a chain reaction of collisions, which can be detected on the Earth's surface as a particle shower. Depending on the energy of the incoming particle, these Extensive Air Showers (EAS) can consist of up to a hundred billion particles within a radius of a few hundreds of meters. From the initial hit down to the Earth's surface, the cascade of collisions takes only a few tens of nanoseconds.

LOFAR-antennas consist of a plastic tube pyramid. An antenna is approximately two meters tall.

The electrons and positrons created in the shower generate radiation in the low frequency radio regime. An important purpose of LOFAR (LOw Frequency ARray) is to detect this radiation.

The radio detection of air showers has been pioneered by the LOPES experiment (LOfar PrototypE Station), located at Forschungszentrum Karlsruhe, on site of the KASCADE-Grande air shower experiment. While radio emission from air showers is recorded with LOPES, the particle component is registered simultaneously with the KASCADE-Grande experiment.

The LOFAR Radboud Air shower array (LORA) is an array of particle detectors in the LOFAR core. Objective is to trigger the antennas of LOFAR when an air shower impinges the LOFAR core and to measure the properties of the air shower.

LORA consists of 20 particle detectors distributed over an area of 300×300 m2 in the LOFAR core. The detectors are plastic scintillators which produce scintillation light when charge particles pass through it. By detecting the secondary charged particles contained in an air shower, we can infer important properties of the primary cosmic ray particle like its energy and arrival direction. The basic detection technique adopted by LORA is well established and well understood so that it can be used as a testbed for the cosmic ray detection with LOFAR.

See the following sites for more information about LOFAR and LOPES:

Information about the LOFAR Cosmic Ray software: