Modeling ice birefringence and oblique radio wave propagation for neutrino detection at the South Pole

• Published in: Annals of Glaciology
• Main Authors: T. M. Jordan, D. Z. Besson, I. Kravchenko, U. Latif, B. Madison, A. Nokikov, A. Shultz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2020
• Subjects: Anisotropic ice; radio-echo sounding; glaciological instruments and methods; ice core; Meteorology. Climatology; QC851-999; South Pole; Annals of Glaciology; South pole
• Online Access: https://doi.org/10.1017/aog.2020.18; https://doaj.org/article/e96ccb45a5154c11a3ba3936695b2caf

The Askaryan Radio Array (ARA) experiment at the South Pole is designed to detect high-energy neutrinos which, via in-ice interactions, produce coherent radiation at frequencies up to 1000 MHz. Characterization of ice birefringence, and its effect upon wave polarization, is proposed to enable range estimation to a neutrino interaction and hence aid in neutrino energy reconstruction. Using radio transmitter calibration sources, the ARA collaboration recently measured polarization-dependent time delay variations and reported significant time delays for trajectories perpendicular to ice flow, but not parallel. To explain these observations, and assess the capability for range estimation, we use fabric data from the SPICE ice core to model ice birefringence and construct a bounding radio propagation model that predicts polarization time delays. We compare the model with new data from December 2018 and demonstrate that the measurements are consistent with the prevailing horizontal crystallographic axis aligned near-perpendicular to ice flow. The study supports the notion that range estimation can be performed for near flow-perpendicular trajectories, although tighter constraints on fabric orientation are desirable for improving the accuracy of estimates.