dc.contributor.author Grillo Csaszar, Gianfranco dc.date.accessioned 2018-10-23T13:22:03Z dc.date.available 2018-10-23T13:22:03Z dc.date.issued 2018-05-30 dc.identifier.other GrilloCsaszar_cornell_0058O_10307 dc.identifier.other http://dissertations.umi.com/cornell:10307 dc.identifier.other bibid: 10489442 dc.identifier.uri https://hdl.handle.net/1813/59357 dc.description.abstract Plasma lensing events can have significant observational consequences, including flux modulations and perturbations in pulse arrival times. In this paper we develop and apply a formalism based on an extension of geometric optics that can be used to describe the effects of two dimensional plasma lenses of arbitrary shape. We apply insights from catastrophe theory and the study of uniform asymptotic expansions of integrals to describe the lensing amplification close to fold caustics and in shadow regions, and explore the effects of image appearance and disappearance at caustics in the TOA perturbations due to lensing. We find that the enhanced geometric optics approach successfully reproduces the predictions from wave optics, and that it can be efficiently used to simulate multifrequency TOA residuals during lensing events. Lensing will introduce perturbations in these residuals that will manifest as an increased spreading in the data points at lower frequencies, and will deviate from the expected dispersive $\nu^{-2}$ scaling most significantly when including observations at low frequencies, $\nu<0.7$ GHz. dc.language.iso en_US dc.subject Astronomy dc.subject ISM dc.subject pulsars dc.subject Plasma lensing dc.subject Optics dc.subject Astrophysics dc.subject scintillation dc.title Wave Asymptotics and their Application to Astrophysical Plasma Lensing dc.type dissertation or thesis thesis.degree.discipline Applied Physics thesis.degree.grantor Cornell University thesis.degree.level Master of Science thesis.degree.name M.S., Applied Physics dc.contributor.chair Lovelace, Richard V. E. dc.contributor.committeeMember Cordes, James Martin dcterms.license https://hdl.handle.net/1813/59810 dc.identifier.doi https://doi.org/10.7298/X4T151XG
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