Bulk and Surface Radio-Frequency Response of Ice

Abstract

The flux and cross section of high energy neutrinos is an active area of research. Due to the expected low flux and cross section, interactions are rare and direct detection is ruled out. Large detector volumes with detection signals that can be observed from far away represent a reasonable and economical way to combat this problem. A currently popular detection strategy is to use a large, dense medium -- such as ice -- for the detector volume and radio antennas as the detectors. These radio antennas are sensitive to Cherenkov radiation produced via the Askaryan effect when a neutrino interacts in the detector volume. To determine the absolute amplitude of radio frequency (RF) emissions from high energy physics processes observed by Antarctic detectors, the bulk attenuation and surface reflection properties of Antarctic ice must be estimated. Neutrino experiments that intend to use polar ice as the detector volume must consider the depth-dependent attenuation length of the ice. Airborne experiments, such as the balloon-borne ANtarctic Impulsive Transient Antenna (ANITA), additionally need to consider the effects of the ice-air transition for both refracted signals produced by neutrino collisions in ice and reflected signals generated by cosmic ray-induced extensive air showers (EAS). Combining radar depth sounding (RDS) data for the estimation of attenuation length with radar scatterometer measurements for the estimation of surface roughness, we seek to create Antarctica-wide attenuation models. Though models and estimates for attenuation and reflection are motivated by ANITA analysis, the methods and results should have general use for the treatment of radio frequency signals interacting with ice and similar media.