Studies of elves and their connection to lightning with the Pierre Auger Observatory

Abstract

Emissions of Light and Very-low frequency perturbations due to Electromagnetic pulse Sources (elves) are observed by the Pierre Auger Cosmic-Ray Observatory (Auger), located in Malargüe, Argentina, with an unprecedented acquisition rate of 10 MHz. An elve is a ring-shaped transient luminous event that expands across the base of the ionosphere at 90 km altitude, above thunderstorms. The elve-observation footprint of the Auger Fluorescence Detector (FD) is 3×10^6 km2, extending over this region known for the highest lightning-flash rate in the tallest thunderstorms on Earth. Northern Argentina has also be identified as one of the only landmasses struck by lightning superbolts, which radiate more than 1 MJ in the form of an electromagnetic pulse. In this dissertation, I first provide background on thunderstorm electrification, lightning processes, and transient luminous events. Second, I present phenomenological properties that I reconstruct directly from the elve data of the Auger FD. I report the first observation of an elve with a complex light spectrum and an elve with a record radial extent of 1000 km. I also reconstruct the lowest altitude intra-cloud lightning stroke ever reported from the observation of elves, 7 km. Third, I detail the end-to-end simulation and perform sensitivity studies of the simulation of the photon surface density of elves to various lightning properties. I employ the elve simulation to estimate the sensitivity of the Auger FD to the altitude of lightning strokes. Fourth, I compare the simulation directly to two well-characterized elves acquired by the Auger FD to assess the validity of the end-to-end simulation. The detailed comparison of well-calibrated data and elaborate simulation will guide future improvements in the current models used to describe elves. From the simulation, I parametrize a relationship between lightning peak current and elve maximum brightness to reconstruct the lightning current of the Auger elve-inducing lightning strokes. Finally, I summarize the major results of this work and how they benefit the field of atmospheric electricity physics.