THE OCTOBER 22, 1989, SOLAR COSMIC-RAY EVENT MEASURED AT GEOSYNCHRONOUS ORBIT

We compare proton measurements (5-150 MeV) made on two geosynchronous satellites during the October 22, 1989 solar cosmic ray event to those from ground-based neutron monitors. The satellite and ground instruments detected similar signatures in the solar protons for this event: an intense initial 'spike' made up of two individual peaks followed by a longer, slower pulse. The height of the spike relative to the pulse was larger for higher measured energies. Most of the differences between the event's characteristics as seen on the ground and in orbit may be attributed to the different energy regimes sampled by the different detectors: < 150 MeV for the satellites, compared to > 450 MeV for the neutron monitors. The existence of the spike at low energies argues against an interpretation of the spike's origin as primary solar neutrons.