Speaker
Description
The upper 100 - 200 m of the polar ice sheet, known as the firn layer, undergoes seasonal variations in density and temperature that modify its refractive index profile. These changes lead to variations in received signal power and arrival time for radio signals propagating through near-surface regions of the firn. In the absence of time-dependent ice models, this introduces an irreducible background uncertainty in the reconstructed energy and arrival direction of neutrinos and cosmic rays for a range of source positions relative to the detector, with variations of $\mathcal{O}(10 \%)$ in signal power and reconstructed energy, and $\mathcal{O}(0.1^{\circ}–1^{\circ})$ in arrival direction. We present a simulation study quantifying the impact of seasonal firn variability on reconstruction performance for both shallow and deep radio neutrino detectors. In addition, we report measurements of ice properties at the Radar Echo Telescope for Cosmic Rays (RET-CR) site in Greenland, combining in-situ density measurements with radar-based reconstructions, and demonstrate how these measurements can be used to constrain ice models for event reconstruction.