Atmospheric Neutrinos, Astrophysical Neutrons, and Proton-Decay Experiments

Simple analytical estimates of the fluxes of atmospheric muons and neutrinos are presented. It is shown that the geomagnetic field strongly suppresses the fluxes of atmospheric neutrinos below 1 GeV from directions of low magnetic latitudes and may open a window for neutrino astronomy. The validity of these estimates is demonstrated through indirect tests.