  In order to optimise the design of space instruments making use of detection
materials with low atomic numbers, an understanding of the atmospheric neutron
environment and its dependencies on time and position is needed. To produce a
simple equation based model, Monte Carlo simulations were performed to obtain
the atmospheric neutron fluxes produced by charged galactic cosmic ray
interactions with the atmosphere. Based on the simulation results the
omnidirectional neutron environment was parametrised including dependencies on
altitude, magnetic latitude and solar activity. The upward- and downward-moving
component of the atmospheric neutron flux are considered separately. The energy
spectra calculated using these equations were found to be in good agreement
with data from a purpose built balloon-borne neutron detector, high altitude
aircraft data and previously published simulation based spectra.
