Light diffusion in birefringent polycrystals and the IceCube ice anisotropy

TL;DR

This paper investigates how the birefringent micro-structure of glacial ice causes anisotropic light diffusion, impacting the optical modeling crucial for neutrino detection in the IceCube observatory.

Contribution

It proposes that ice's birefringent polycrystal structure explains the observed anisotropic light attenuation in IceCube.

Findings

Birefringence in ice affects light propagation.

Anisotropic attenuation aligns with ice flow.

Micro-structure influences optical properties.

Abstract

The IceCube Neutrino Observatory instruments about 1 km^3 of deep, glacial ice at the geographic South Pole with 5160 photomultipliers to detect Cherenkov light from charged relativistic particles. The experiment pursues a wide range of scientific questions ranging from particle physics such as neutrino oscillations to high-energy neutrino astronomy. Most of these efforts rely heavily on an ever more precise understanding of the optical properties of the instrumented ice. An unexpected light propagation effect, observed by the experiment, is an anisotropic attenuation, which is aligned with the local flow of the ice. The exact cause is still under investigation. In this contribution, the micro-structure of ice as a birefringent polycrystal is explored as the cause for this anisotropy.