Clusters of such neutrino directions indicate point sources of neutrinos. Each of the above steps requires a certain minimum energy, and thus IceCube is sensitive mostly to high-energy neutrinos, in the range of 10⁷ to about 10²¹ eV.

High-energy astrophysical events Neutrinos can either be primary cosmic rays (astrophysical neutrinos), or be produced from cosmic ray interactions. In the latter case, the primary cosmic ray will produce pions and kaons in the atmosphere. As these hadrons decay, they produce neutrinos (called atmospheric neutrinos).