Radio-Emission from Atmosphere-Skimming Cosmic-Ray Showers in High-Altitude Balloon-Borne Experiments

M. TUEROS (COAUTOR); S. CABANA-FREIRE; J. ALVAREZ-MUÑIZ

Nagoya

Conferencia; 38th International Cosmic Ray Conference; 2023

Institute for Cosmic Ray Research (ICRR), University of Tokyo, Japan - IUPAP

Atmosphere-skimming showers are initiated by cosmic rays above the Earth’s horizon with incoming directions such that the development of the cascade occurs fully inside the atmosphere. Radiopulses induced by this type of showers have already been observed in balloon-borne experimentssuch as ANITA, but a characterization of their properties is lacking. The extreme range of densities in which these cascades can develop gives rise to a wide range of shower profiles, with characteristics of the radio emission that can differ significantly from those of regular downward-going showers. To study this type of event, we have used the ZHAireS-RASPASS program, a custom-built modification to the well-known ZHAireS suite capable of simulating atmosphere-skimming showers and calculating their associated radio emission. We have studied the interplay betweenthe magnetic field and atmospheric density profile in the expected signal, focusing on the detection of these events by experiments flying over Antarctica. A new asymmetry in the spatial distribution of the electric field has been identified as a consequence of the very long distances over which the shower particles propagate in the Earth’s magnetic field (the coherence asymmetry). This asymmetry adds to (but is independent of) the already expected diffractive asymmetry, that is a consequence of the propagation of the radio signal through an index of refraction gradient. Finally we briefly discuss the implications of these peculiar characteristics on the expected exposure of balloon-borne experiments, and provide an estimation of the most probable energy for events detected by ANITA IV