Radio detection of cosmic rays with LOFAR

Stijn Buitink


LOFAR is a multipurpose radio telescope which can be used for radio detection of cosmic ray air showers while running astronomical observations at the same time. The core of LOFAR contains 2300 antennas within an area of four square kilometer. This high density makes it an ideal location for a detailed study of the radio signal of extensive air showers in the energy range 10$^{16}$ - 10$^{18}$ eV.

We present the first analyses of high quality LOFAR events for which the lateral distribution of the radio signal can be studied in full 2D. Radio and particle data shows excellent agreement with simulation, indicating that the complicated emission mechanism is finally well-understood. Moreover, the depth of the shower maximum (Xmax) can be inferred with an accuracy that is comparable to the fluorescence detection technique. This proofs that radio detection can be used for cosmic ray composition studies and is an excellent technique to complement air shower arrays like Auger and other (future) experiments..