Detecting cosmic rays with the LOFAR radio telescope

Abstract

The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first ~{}2 years of observing, 405 cosmic-ray events in the energy range of 10$^{16}$-10$^{18}$ eV have been detected in the band from 30-80 MHz. Each of these air showers is registered with up to ~{}1000 independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.