Exploration of cosmic-ray propagation and thunderstorm models to explain unusual events measured with the surface detector of the Pierre Auger Observatory

Abstract

The Surface Detector at the Pierre Auger Observatory has recorded events that have an unusually large footprint on the array and lasts 100 times longer than a typical cosmic ray signal. This thesis explores possible models to explain the source of these unusual signals. The proposed models show that the unusual signals are not a result of a cosmic ray shower but are instead likely a result of a lightning-related phenomenon. The attachment process and the return stroke can create E-fields strong enough to create runaway relativistic electron avalanches. This process creates a cascade of high energy electrons that can span over 100 meters and induces high energy photons that can travel a few kilometers. The Surface Detector would be able to measure the high energy particles resulting from this runaway process. The simulated model of the return stroke produced a signal on the ground that was able to match the long-time of the unusual events. This very preliminary model provides some insights for some of the unusual events, but a complete explanation for the events remains elusive.