Long-baseline horizontal radio-frequency transmission through polar ice

TL;DR

This study analyzes long-distance radio-frequency signals transmitted through polar ice, confirming extended attenuation lengths, timing models, and birefringent asymmetries, which are crucial for neutrino detection and ice sheet studies.

Contribution

It provides new measurements of RF signal propagation, attenuation, and birefringence in polar ice over long baselines, using novel deep ice transmitters and multiple receiver stations.

Findings

RF electric field attenuation length exceeds 1 km

Observed birefringent asymmetries at 0.15% level

Timing distributions match propagation models

Abstract

We report on analysis of englacial radio-frequency (RF) pulser data received over horizontal baselines of 1--5 km, based on broadcasts from two sets of transmitters deployed to depths of up to 1500 meters at the South Pole. First, we analyze data collected usingtwo RF bicone transmitters 1400 meters below the ice surface, and frozen into boreholes drilled for the IceCube experiment in 2011. Additionally, in Dec., 2018, a fat-dipole antenna, fed by one of three high-voltage (~1 kV), fast (~(1-5 ns)) signal generators was lowered into the 1700-m deep icehole drilled for the South Pole Ice Core Experiment (SPICE), approximately 3 km from the geographic South Pole. Signals from transmitters were recorded on the five englacial multi-receiver ARA stations, with receiver depths between 60--200 m. We confirm the long, >1 km RF electric field attenuation length, test our observed signal arrival timing distributions against models, and measure birefringent asymmetries at the 0.15% level.