A Model of the Cosmic Ray Induced Atmospheric Neutron Environment

TL;DR

This paper develops a simple, parameterized model of atmospheric neutron fluxes caused by cosmic rays, considering altitude, latitude, and solar activity, validated against experimental data.

Contribution

It introduces a new equation-based model for atmospheric neutron fluxes that accounts for various environmental dependencies and matches observed data.

Findings

Model accurately predicts neutron fluxes across different conditions.

Good agreement with balloon, aircraft, and previous simulation data.

Provides a useful tool for designing space instruments.

Abstract

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.