Spectral characteristics of low-frequency variability in compact extragalactic radio sources

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dc.contributor.authorPantazopoulou, Maria J.en
dc.contributor.committeechairDennison, Brianen
dc.contributor.committeememberChang, Lay Namen
dc.contributor.committeememberMo, Luke W.en
dc.contributor.committeememberDeWolf, David A.en
dc.contributor.committeememberSimonetti, John H.en
dc.contributor.departmentPhysicsen
dc.date.accessioned2014-03-14T21:22:33Zen
dc.date.adate2005-10-26en
dc.date.available2014-03-14T21:22:33Zen
dc.date.issued1996en
dc.date.rdate2005-10-26en
dc.date.sdate2005-10-26en
dc.description.abstractWe examine the refractive scintillation hypothesis of low frequency variability via numerical simulation in order to account for the spectral characteristics of the observed fluctuations. Plane waves from extragalactic radio sources propagating through the interstellar medium, a medium with fluctuations of the refractive index due to electron density irregularities, emerge from that medium corrugated. Since fluctuations present on scales greater than the Fresnel scale act refractively, the emerging wavefront has a curvature which produces a refractive amplification or deamplification in the flux density. We develop a numerical algorithm to characterize the phase fluctuations in the wavefront and we simulate the resulting intensity distribution in the limit of geometrical optics. We then produce light curves by taking trajectories in the simulated intensity distribution plane and we compare our results with statistical properties of existing data from a 5—year monitoring program of 32 extragalactic sources at frequencies 0.318, 0.430, 0.606, 0.880 and 1.4 GHz. We find that the refractive scintillation hypothesis is in good agreement with the data at comparable timescales and that the variability in the simulated light curves diminishes within an octave of frequency, in agreement with those of the observed light curves with the same behavior.en
dc.description.degreePh. D.en
dc.format.extentviii, 142 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-10262005-143540en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10262005-143540/en
dc.identifier.urihttp://hdl.handle.net/10919/40238en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1996.P368.pdfen
dc.relation.isformatofOCLC# 35832140en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1996.P368en
dc.titleSpectral characteristics of low-frequency variability in compact extragalactic radio sourcesen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplinePhysicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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