Measurement of horizontal air showers with the Auger Engineering Radio Array

TL;DR

This paper reports on the measurement of horizontal air showers using the Auger Engineering Radio Array, demonstrating the detection of very inclined showers and confirming simulation predictions, with implications for cosmic ray and neutrino detection.

Contribution

The study extends radio detection capabilities to horizontal air showers up to 80° zenith angle, confirming simulation predictions and opening new avenues for cosmic ray and neutrino research.

Findings

Radio footprints of horizontal showers are several km$^2$ in size.

AERA successfully detects very inclined air showers.

Results support future radio-based composition and energy measurements.

Abstract

The Auger Engineering Radio Array (AERA), at the Pierre Auger Observatory in Argentina, measures the radio emission of extensive air showers in the 30-80 MHz frequency range. AERA consists of more than 150 antenna stations distributed over 17 km$^2$. Together with the Auger surface detector, the fluorescence detector and the under-ground muon detector (AMIGA), AERA is able to measure cosmic rays with energies above 10$^{17}$ eV in a hybrid detection mode. AERA is optimized for the detection of air showers up to 60$^{\circ}$ zenith angle, however, using the reconstruction of horizontal air showers with the Auger surface array, very inclined showers can also be measured. In this contribution an analysis of the AERA data in the zenith angle range from 62$^{\circ}$ to 80$^{\circ}$ will be presented. CoREAS simulations predict radio emission footprints of several km$^2$ for horizontal air showers, which are now confirmed by AERA measurements. This can lead to radio-based composition measurements and energy determination of horizontal showers in the future and the radio detection of neutrino induced showers is possible.