Implications of Biaxial Birefringence for the Askaryan Radio Array

The Askaryan Radio Array (ARA) is an experiment with the goal of detecting ultra-high energy (>10 PeV) neutrinos at the South Pole for the first time. ARA uses arrays of antennas designed to detect radio-frequency radiation emitted from relativistic particle showers produced by neutrinos interacting within the ice. South Pole ice is biaxially birefringent, causing the polarization of signals to rotate during propagation and to split into two rays propagating at different speeds. These effects depend on the signal's direction and polarization. Modeling the effects of birefringence is necessary to ascertain the polarization where the radio signal was emitted. In addition, the time delay between the two rays is a signature of an in-ice interaction and provides information about the distance to the interaction, an ingredient in energy reconstruction that is the most difficult to measure. Quantifying effects from birefringence is also relevant for antenna design optimization. In this talk, I will discuss birefringence modeling for ARA, their impact on polarization measurements, and antenna design.