Trapped proton and cosmic-ray albedo neutron fluxes

Abstract

A nuclear emulsion stack was flown on an Atlas vehicle on October l3, 1960. The vehicle went to a maximum altitude of ll85 km. Protons with energies above l7 Mev were measured. The number of protons/(cm/sup 2/)(sec)(Mev) between l000 and ll85 km is 0.6 plus or minus 0.1 of the value obtained on a previous flight of April 7, l959, between the altitudes of l000 and l230 km. The energy distribution is in excellent agreement with that measured on the April 7 flight. The maximum in the energy distribution at 75 Mev observed in July l959 is no longer visible. At 30 Mev, the energy distribution departs from the theoretical distribution which is calculated using the cosmic-ray albedo neutron decay source and ionization and nuclear collision loss mechanisms. This deviation is probably due to a minimum in the albedo neutron energy distribution caused by a large neutron nonelastic cross seetion in nitrogen and oxygen at about 20 Mev; the proton energy distribution should rise rapidly below l0 Mev to meet the theoretical curve. The expenimental data also fall below the theoretical curve at above 300 Mev. This deviation may be caused by additional loss mechanisms that preferentially affect the high-energy protons, such as the breakdown of the adiabatic eondition or the presence of hydromagnetic waves. It may also be due to a trapping probability that decreases with increasing energy or to a neutron energy distribution that drops off more rapidly with energy than the E-/ used in the calculation. The albedo neutron energy spectrum is derived assuming it is the only source of the trapped protons and the only loss mechanisms are ionization and nuclear collisions.