Low-energy atmospheric neutrinos

Results of a three-dimensional Monte Carlo calculation of the low-energy spectrum and angular distribution of atmospheric neutrinos are presented and compared with earlier one-dimensional calculations valid at higher neutrino energies. The three-dimensional results agree with the one-dimensional calculation above 200 MeV, but are up to a factor of 2 lower below 50 MeV. Geomagnetic-cutoff effects on primary cosmic rays significantly reduce the neutrino flux at low geomagnetic latitudes. Azimuthal angular dependence shows a strong north-south asymmetry for upward-going fluxes, whereas an east-west effect is apparent only at low geomagnetic latitudes.