Reflections on the anomalous ANITA events: the Antarctic subsurface as a possible explanation

• Published in: Annals of Glaciology
• Main Authors: Ian M. Shoemaker, Alexander Kusenko, Peter Kuipers Munneke, Andrew Romero-Wolf, Dustin M. Schroeder, Martin J. Siegert
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2020
• Subjects: Antarctic glaciology; Ice physics; Snow physics; Meteorology. Climatology; QC851-999; Antarctic; The Antarctic; Annals of Glaciology; Antarc*
• Online Access: https://doi.org/10.1017/aog.2020.19; https://doaj.org/article/2df485aba40a4013b3afd3ae6544d9b1

The Antarctic Impulsive Transient Antenna (ANITA) balloon experiment was designed to detect radio signals initiated by high-energy neutrinos and cosmic ray (CR) air showers. These signals are typically discriminated by the polarization and phase inversions of the radio signal. The reflected signal from CRs suffer phase inversion compared to a direct ‘tau neutrino’ event. In this paper, we study subsurface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by ANITA. It is found that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. This hypothesis can be tested with radar surveying of the Antarctic region in the vicinity of the anomalous ANITA events. Future experiments should not use phase inversion as a sole criterion to discriminate between down-going and up-going events, unless the subsurface reflection properties are well understood.