Let me clarify, as someone involved in writing this paper.

This radio emisison (Askaryan emission) is the mechanism by which we hope to detect neutrinos with detectors like ARA (and also PUEO, RNO-G, etc. which I also work on :) ), but these events are actually candidate impacting cosmic rays. UHE cosmic rays (protons, and heavier nuclei) are charged particles that will start cascading in the atmosphere, but in certain near- vertical geometries, the shower is not "expended" before reaching the ice (which lies at an altitude of ~3km), so the dense shower core enters the ice, producing radio emission from the same mechanism through which we hope to detect neutrinos. While the Askaryan mechanism was detected in ice in beam line experiments and also in the atmosphere (where it is subdominant to radio emission from charged particles bending in the Earth's magnetic field), this is the first detection of the Askaryan effect in natural ice, proving that the emission matches our models. The cosmic rays themselves are not super interesting in the sense that there are other detectors that are much better at detecting cosmic rays (e.g .TA or Pierre Auger).