Theses and Dissertations at Montana State University (MSU)
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Item Investigations of the properties of radiation belt electron precipitation observed by the FIREBIRD-II CubeSats(Montana State University - Bozeman, College of Letters & Science, 2022) Johnson, Arlo Thomas; Chairperson, Graduate Committee: John Sample; This is a manuscript style paper that includes co-authored chapters.High energy electrons can be trapped by the Earth's magnetic field in regions known as the radiation belts. Some of these electrons will impact the upper atmosphere and be lost from the radiation belt system in a process known as electron precipitation. This dissertation explores two questions regarding electron precipitation using data from the focused investigations of relativistic electron burst intensity, range, and dynamics II CubeSat mission. The first question was to determine the energy dependence of specific type of impulsive precipitation known as a microburst, which may be a significant contributer to electron loss from the radiation belts. A statistical study of several hundred microbursts was performed and the energy spectrum was found to generally be exponential with a wide rage of possible parameters depending in part on the level of geomagnetic activity. In addition, comparison of this spectrum with the rest of the radiation belt population revealed that microbursts are a more effective loss mechanism for electrons with relatively lower energies. The second question addresses the possibility of inducing electron precipitation using magnetospheric waves artificially generated by a spacecraft. Waves of 3.0 or 8.2 kHz were excited in the magnetosphere by the Demonstration and Science Experiments satellite and a related signature was searched for in the precipitating electrons. There was no evidence of additional precipitating electrons, so an sensitivity estimate was carried out to place boundaries on the diffusion rates needed to create a measurable precipitation signature. It was found that in many cases a diffusion rate similar to those driven by naturally occurring waves was required, but in cases with a high number of electrons available to interact with the waves the diffusion rates could be orders of magnitude weaker and still produce a measurable amount of precipitation.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.