Where are the IceCube high-energy astrophysical neutrinos coming from? We don’t know yet! But if the neutrino sources harbor large magnetic fields, then maybe they will leave imprints (due to synchrotron radiation) on the neutrino flux. We looked for these imprints in public IceCube data:
Using High-Energy Neutrinos As Cosmic Magnetometers
Mauricio Bustamante & Irene Tamborra
https://arxiv.org/abs/2009.01306
We exclude large magnetic fields of 10 kG–10 MG:
Mauricio Bustamante 