Relativistic solar neutrons and protons on 28 October 2003 -: art. no. L03S02

The solar cosmic ray event associated with the X17.2 class flare of 28 October 2003 was unusual in several respects: ( 1) Several high-latitude neutron monitors observed a large, highly anisotropic spike at event onset. ( 2) The earliest onset was detected by stations viewing towards the anti-Sunward hemisphere. ( 3) The event displayed an extremely slow, protracted decay. ( 4) The near-equatorial monitor in Tsumeb, Africa recorded a small increase consistent with a solar neutron event approximate to7 minutes prior to the onset at high latitudes. We analyze these signals and infer that relativistic solar neutrons were emitted over a duration of approximate to9 minutes, starting approximate to7 minutes before the main injection of relativistic protons.