Measurement of Radio Emission from Extensive Air Showers with LOPES

A new method is explored to detect extensive air showers: the measurement of radio waves emitted during the propagation of the electromagnetic shower component in the magnetic field of the Earth. Recent results of the pioneering experiment LOPES are discussed. It registers radio signals in the frequency range between 40 and 80 MHz. The intensity of the measured radio emission is investigated as a function of different shower parameters, such as shower energy, angle of incidence, and distance to shower axis. In addition, new antenna types are developed in the framework of LOPES-Star and new methods are explored to realize a radio self-trigger algorithm in real time.

💡 Research Summary

The paper presents the LOPES (LOFAR Prototype Station) experiment, which explores a novel technique for detecting extensive air showers (EAS) by measuring the radio emission generated as the electromagnetic component of the shower propagates through the Earth’s magnetic field. LOPES operates in the 40–80 MHz band, a relatively quiet window with few strong man‑made transmitters and low Galactic background, making it suitable for observing the weak radio pulses from air showers. The array consists of 30 inverted V‑shaped short dipole antennas co‑located with the KASCADE‑Grande particle detector at the Karlsruhe Institute of Technology. Each antenna, together with its analog front‑end, is individually calibrated using a reference radio source, enabling absolute field‑strength measurements in µV m⁻¹ MHz⁻¹.

The authors correlate the measured radio signal with shower parameters provided by KASCADE‑Grande (energy, core position, zenith and azimuth angles). They derive an empirical formula for the east‑west component of the electric field ε at a distance R from the shower axis:

ε = (11 ± 1)