Theses and Dissertations at Montana State University (MSU)
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Item Relating terrestrial gamma-ray flash production to associated lightning and thunderstorm characteristics(Montana State University - Bozeman, College of Letters & Science, 2022) Larkey, Reyann Kathleen; Chairperson, Graduate Committee: John Sample; This is a manuscript style paper that includes co-authored chapters.Terrestrial Gamma-ray Flashes (TGFs) are puzzling, but potentially hazardous bursts of high-energy radiation associated with the everyday phenomena of lightning. Not every lightning flash produces a TGF, however, and the question of what makes a TGF-associated lightning flash different is not well understood. This dissertation investigates this question by examining how TGF production is related to thunderstorm characteristics such as inter-flash intervals, flash rate trends, and flash amplitudes. Additionally, investigation into the precise timing relationship between TGFs and stroke signatures in their associated lightning flash is also presented. The conclusions of these studies show that TGFs are most likely to occur after longer than usual charge-up times, when the flash rates tend to be declining in storms, and when amplitudes of flashes are stronger than normal. The last study also details the presence of two distinct excess peaks of delayed lightning signals occurring after TGFs compared to other non-TGF flashes. This study examines the amplitudes of these delayed lightning signals and compares those signals to the entire distribution of non-TGF strokes. These findings hint that TGF-production may be the result of unusually complex lightning flashes. However, further research into these peaks requires additional data from other spacecraft and perhaps updated TGF catalogs to examine the context of these lightning flashes. Nonetheless, this initial study may further help explain why TGFs are not produced in association with all lightning flashes.Item Connecting microburst precipitation to its scattering mechanism(Montana State University - Bozeman, College of Letters & Science, 2019) Shumko, Mykhaylo Sergeevich; Chairperson, Graduate Committee: John Sample; Drew L. Turner, T. P. O'Brien, Seth G. Claudepierre, John Sample, D. P. Hartley, Joseph Fennell, J. Bernard Blake, Matina Gkioulidou and Donald G. Mitchell were co-authors of the article, 'Evidence of microbursts observed near the equatorial plane in the outer Van Allen Radiation Belt' in the journal 'Geophysical research letters' which is contained within this thesis.; John Sample, Arlo Johnson, Bern Blake, Alex Crew, Harlan Spence, David Klumpar, Oleksiy Agapitov and Matthew Handley were co-authors of the article, 'Microburst scale size derived from multiple bounces of a microburst simultaneously observed with the Firebird-II cubesats' in the journal 'Geophysical research letters' which is contained within this thesis.; A.T. Johnson, J.G. Sample, B.A. Griffith, D.L. Turner, T.P. OBrien, O. Agapitov, J.B. Blake and S. G. Claudepierre were co-authors of the article, 'Microburst size distribution derived with Aerocube-6' submitted to the journal 'Geophysical research letters' which is contained within this thesis.We will review the main structures in the magnetosphere, the motion of charged particles in electric and magnetic fields, how particles are accelerated and lost in the magnetosphere, and asses the current state of our understanding of microbursts. Then the rest of this dissertation expands our knowledge of microbursts. In Chapter 2 we will investigate and model the scattering mechanism responsible for microbursts observed inside the outer radiation belt, near the magnetic equator. Then in Chapters 3 and 4 we will investigate the microburst scattering mechanism indirectly by estimating the microburst footprint size in low Earth orbit and the magnetic equator (near where microburst electrons are believed to be scattered) and compare it to sizes of chorus waves estimated in prior literature.