Impact of biaxial birefringence in polar ice at radio frequencies on signal polarizations in ultra-high energy neutrino detection

• Main Author: Connolly, Amy
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: arXiv 2021
• Subjects: Instrumentation and Methods for Astrophysics astro-ph.IM; High Energy Astrophysical Phenomena astro-ph.HE; FOS Physical sciences; Antarctic; South Pole; The Antarctic; Antarc*; Ice Sheet; South pole
• Online Access: https://dx.doi.org/10.48550/arxiv.2110.09015; https://arxiv.org/abs/2110.09015

It is known that the Antarctic ice sheet is birefringent and that this can have implications for in-ice radio detection of ultra-high energy neutrinos. Previous investigations of the effects of birefringence on the propagation of radio-frequency signals in ice have found that it can cause time delays between pulses in different polarizations in in-ice neutrino experiments, and can have polarization-dependent effects on power in radar echoes at oblique angles in polar ice. I report, for the first time, on implications for the received power in different polarizations in high energy neutrino experiments, where the source of the emitted signal is in the ice, a biaxial treatment at radio wavelengths is used, and the signals propagate at oblique angles. I describe a model for this and validate it against published results from the SPICE in-ice calibration pulser system at South Pole, where unexpectedly high cross-polarization power has been reported for some geometries. The data shows behaviors consistent with a biaxial treatment of birefringence inducing non-trivial rotations of the signal polarization. These behaviors include, but are not limited to, an interference effect that would leave an imprint in the power spectrum. This would serve as both an in-ice neutrino signature and a measurement of the distance to the interaction. While further work is needed, I expect that proper handling of the effects presented here will increase the science potential of ultra-high energy neutrino experiments, and may impact the optimal designs of next-generation detectors. : 21 pages, 13 figures. Submitted to PRD