Measurements of the atmospheric neutron leakage rate

Abstract

The atmospheric neutron leakage rate in the energy range 10−2 to 107 ev has been measured as a function of latitude, altitude, and time with a neutron detector on board the Ogo 6 satellite. The latitude dependence of the neutron leakage is in reasonable agreement with that predicted by R. E. Lingenfelter and E. S. Light et al. if the neutron energy spectrum has the shape calculated by L. L. Newkirk. The change in the neutron latitude dependence with the cosmic ray modulation agrees with the predictions of Lingenfelter and Light et al. For several solar proton events enhancements were observed in the neutron counting rates at λ ≥ 70°. Such events, however, provide an insignificant injection of protons at E ≤ 20 Mev into the radiation belts. An isotropic angular distribution of the neutron leakage in the energy range 0.1 kev to 10 Mev best fits the observed altitude dependence of the neutron leakage flux.

The low Earth orbit radiation environment and its impact on the prompt background of hard x-ray focusing telescopes

“…As for γ-rays and charged particles, the source for atmospheric neutrons is the impinging GCR flux, except than at the higher latitude regions (λ m > 70 • ) where also solar protons contribute [40]. The mechanism for neutron production is mainly spallation of nitrogen and oxygen nuclei by GCR collisions and secondary intranuclear cascades [41,42].…”

Measurement of the solar diurnal anisotropy of the cosmic-ray albedo neutron flux

“…First, in order to minimize the local production effects, the neutron counting rates (-10 MeV) were derived from those events in the He 3 proportional counter not associated with events in the charged particle counters, and the neutron counting rates for a particular location were those for which the associated total charged particle rates were less than twice the minimum for that location; all the neutron counting rates were then corrected for dead time and for locally produced neutrons and highly ionizing charged particles by the techniques described by Ifedili (1972). Secondly, the neutron data were limited to geomagnetic latitudes less than 5 ~ since solar proton albedo neutrons do not penetrate to such low latitudes (Ifedili, 1972;Lockwood et al, 1973a;Ifedili, 1979) and since at this location the solar cycle variation and Forbush decrease effects did not significantly affect the albedo neutron flux measured by OGO-6 (Ifedili, 1973). Finally, the neutron counting rates were reduced to 450 km altitude using the observed altitude dependence of the neutron counting rate (Ifedili, 1972;Lockwood et al, 1973a).…”

“…Secondly, the neutron data were limited to geomagnetic latitudes less than 5 ~ since solar proton albedo neutrons do not penetrate to such low latitudes (Ifedili, 1972;Lockwood et al, 1973a;Ifedili, 1979) and since at this location the solar cycle variation and Forbush decrease effects did not significantly affect the albedo neutron flux measured by OGO-6 (Ifedili, 1973). Finally, the neutron counting rates were reduced to 450 km altitude using the observed altitude dependence of the neutron counting rate (Ifedili, 1972;Lockwood et al, 1973a).…”

“…It is pertinent to point out that there were no significant solar neutron effects on the neutron data since no solar neutrons were observed by OGO-6 during quiet time (Lockwood et al, 1973b) and during solar flares (Ifedili, 1974).…”

Atmospheric Neutrons and Their Contributions to the Earth's Radiation Belts.

“…1. Comparison of the observed trapped proton flux at L=1.5 (FREDEN et at., 1965;FILLius and MCILWAI`N, 1964;VALOT, 1972) with that predicted by GRAND using the recent cosmic ray albedo neutron measurements (JENKINS et at., 1970(JENKINS et at., , 1971LocKwooD et at., 1973LocKwooD et at., , 1976IFEDILI 1972IFEDILI ,1982WHITE et at., 1972;KANBACH et at., 1974;PRESZLER et at., 1976). …”