In situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory
Rasha Abbasi, M. Ackermann, Jenni Adams, Nakul Aggarwal, Juanan Aguilar, M. Ahlers, Maryon Ahrens, Jean-Marco Alameddine, A. A. Alves, Najia Moureen Binte Amin, K. Andeen, Tyler Anderson, G. Anton, C. Argüelles, Yosuke Ashida, Sofia Athanasiadou, Spencer Axani, X. Bai, Aswathi Balagopal, Moreno Baricevic, S. W. Barwick, Vedant Basu, Ryan Bay, J. J. Beatty, Karl H. Becker, J. Becker Tjus, Jakob Beise, Chiara Bellenghi, Samuel Benda, S. BenZvi, D. Berley, E. Bernardini, D. Besson, G. Binder, D. Bindig, E. Blaufuss, Summer Blot, Federico Bontempo, Julia Book, Jürgen Borowka, Caterina Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, Etienne Bourbeau, Jim Braun, Bennett Brinson, Jannes Brostean-Kaiser, Ryan T. Burley, Raffaela Busse, Michael Campana, Erin Carnie-Bronca, Chujie Chen, Zheyang Chen, D. Chirkin, K. Choi, Brian Clark, Lew Classen, Alan Coleman, Gabriel Collin, A. Connolly, J. M. Conrad, Paul Coppin, Pablo Correa, S. T. Countryman, D. F. Cowen, R. Cross, Christian Dappen, Pranav Dave, C. De Clercq, James DeLaunay, Diyaselis Delgado Lopez, H.-P. Dembinski, Kunal Deoskar, Abhishek Desai, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, Alejandro A. Díaz, J. C. Díaz–Vélez, Markus Dittmer, Hrvoje Dujmović, M. A. DuVernois, Thomas Ehrhardt, P. Eller, Ralph Engel, Hannah Erpenbeck, John Evans, P. A. Evenson, Kwok Lung Fan, A. R. Fazely, Anatoli Fedynitch, Nora Feigl, Sebastian Fiedlschuster, Aaron Fienberg, C. Finley, Leander Fischer, D. B. Fox, A. Franckowiak
Abstract
Abstract. The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. We examine birefringent light propagation through the polycrystalline ice microstructure as a possible explanation for this effect. The predictions of a first-principles model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties include not only the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube light-emitting diode (LED) calibration data, the theory and parameterization of the birefringence effect, the fitting procedures of these parameterizations to experimental data, and the inferred crystal properties.