Characteristics of atmosphere-skimming air showers relevant for high-altitude radio experiments.

Atmosphere-skimming air showers are initiated by cosmic rays with incoming directions located above the Earth’s horizon, such that the development of the cascade occurs exclusively in the atmosphere. In this work, we have performed a first characterisation of atmosphere skimming particle cascades and their associated radio emission using the ZHAireS-RASPASS simulation program. Both the low air density and the orientation of the magnetic field in the region where the shower development takes place are shown to alter the longitudinal and lateral evolution of the particle cascade depending on its geometry. Significant differences in the radio emission appear as a consequence with respect to downward-going air showers, giving rise to unique features whose impact is discussed regarding the exposure of high-altitude detectors and the interpretation of collected data.