Observation of solar neutrons associated with the large flare on 1991 June 4

Abstract

Evidence for neutrons coming from the sun associated with a large flare at 03:37 UT on 1991 June 4 is reported. The event was recorded by a neutron telescope, and also by a muon telescope, located at Mount Norikura Cosmic Ray Laboratory (2770 m). The statistical significance of the signal recorded by the neutron telescope is 4.4 sigma for neutron kinetic energies between 50 and 360 MeV in the time interval 03:46-03:49 UT. For the muon telescope the statistical significance of the signal is 4.9 sigma in the time interval 03:47-03:56 UT.