Authors: Du Toit Strauss (Centre for Space Research)

Neutron monitors (NMs) are ground-based detectors used for more than 50 years to (indirectly) measure the flux of incoming cosmic ray (CR) particles. With the implementation of new and faster data acquisition systems, it has become possible to digitize individual NM pulses down to <1ms temporal resolution. In this work we use such a new system to calculate the waiting time distributions (i.e. the distribution of elapsed time between subsequent pulses) observed at SANAE, a NM64 detector in Antarctica. Two populations are clearly distinguishable in the waiting time distribution and the ratio of these two populations can, in principle, be related to the spectral index of the incoming radiation. Here we focus on accurately describing and measuring these populations and calculating their pressure (or altitude) dependence. We then apply this technique to two recent (and unfortunately very small) ground level enhancements (GLEs) to search for any indications of spectral changes.