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

• Published in: Annals of Glaciology
• Main Authors: Shoemaker, Ian M., Kusenko, Alexander, Munneke, Peter Kuipers, Romero-Wolf, Andrew, Schroeder, Dustin M., Siegert, Martin J.
• Other Authors: Physics
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2020
• Subjects: Antarctic glaciology; Ice physics; Snow physics; Antarc*; Antarctic
• Online Access: http://hdl.handle.net/10919/98817; https://doi.org/10.1017/aog.2020.19

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. The work of I.M.S. is supported by the US Department of Energy under the award number DE- SC0020250. The work of A.K. was supported by the US Department of Energy Grant No. DE-SC0009937, and by the World Premier International Research Center Initiative (WPI), MEXT, Japan. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. P.K.M. is supported by the Netherlands Earth System Science Centre (NESSC).