Space weather poses a multitude of hazards to human infrastructure and activities on Earth and in space. One such hazard is atmospheric radiation induced by relativistic solar energetic particles. Atmospheric radiation is of particular concern for aviation, as it damages the biological tissue of passengers and crew, and can cause upsets in avionic systems. The risk is greatly increased during the Ground Level Enhancements (GLE) caused by space weather.

Monitoring atmospheric radiation levels is fundamental to mitigating the risk posed by this hazard. There are very few radiation detectors on board aircraft, and monitoring efforts rely heavily on the ground level neutron monitor network. This is a relatively sparse network of detectors ( 50 worldwide) which measure changes in the ground level nucleonic radiation flux. The Cosmic Ray Neutron Sensing (CRNS) method measures soil moisture using small neutron detectors positioned above the soil. There are over 200 such detectors worldwide, including 50 in the UK network alone (COSMOS-UK). The objective of this work is to develop an understanding of how these detectors respond to energetic particles in space and predict how detectors and networks would respond to a GLE. The data from COSMOS-UK has been analysed and signatures of cosmic ray modulation have been identified. No GLEs have been observed, but none have occurred during the lifetime of the network which were of sufficient intensity to be detectable. Additionally, an approximate correction factor for soil moisture was developed, and an indoor CRNS detector station was set up in Guildford, UK. This station is also shown to be able to observe cosmic ray modulation. The response functions of the CRS 2000/B detectors have been calculated, and the models validated against experimental data. The yield function of these detectors have also been calculated and used to successfully predict the long term trend in of COSMOS-UK detectors. Finally, the response of a hypothetical world-wide CRNS network to historical GLEs has been calculated. This demonstrates that CRNS detectors can be used to monitor space weather, particularly GLEs.