Upper limit to the 1?20 MeV solar neutron flux

The upper limit on the quiet time solar neutron flux from 1–20 MeV has been measured to be less than 2 × 10-3n cm-2 s−1 at the 95% confidence level. This result is deduced from the OGO-6 neutron detector measurements of the ‘day-night’ effect near the equator at low altitudes for the period from June 7, 1969, to December 23, 1969. The OGO-6 detector had very low (< 4%) counting rate contributions from locally produced neutrons in the detecting system and the spacecraft and from charged-particle interactions in the neutron sensor.