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Min-Chang Lee and Richard Temkin. Cohen, Joel (Joel A.), S.B. Massachusetts Institute of Technology Massachusetts Institute of Technology. Dept. of Physics. Massachusetts Institute of Technology. Department of Physics 2008-03-27T18:21:35Z 2008-03-27T18:21:35Z 2007 2007 http://hdl.handle.net/1721.1/40903 209876426 Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007. Includes bibliographical references (p. 43). The thermal filamentation instability has been invoked to explain the formation of parallel plate waveguides in mid-latitude ionospheric plasmas during Arecibo, Puerto Rico heating experiments in 1997. The geometry of the kilometer-scale parallel plates predicted by thermal filamentation depends on the mode of the transmitted heater wave, as does the threshold to excite this instability. While plasma heating can excite small-scale irregularities via parametric instabilities, thermal filamentation is thought to produce large-scale irregularities. In Arecibo, the threshold for X-mode to induce irregularities was found to be greater than 1 V/m, while for O-mode it was on the order of mV/m. In recent plasma experiments in high-latitude ionospheric plasmas, carried out at the HAARP facility in Gakona, Alaska in summer 2005, spring 2006, and summer 2006, a weakening in ionogram traces was observed during O-mode and X-mode heating, leading to a scenario detailing the effects of thermal filamentation and short-scale irregularities caused by heating. The Gakona experiments using a high power HF heating facility and multiple diagnostic instruments shed light on the important role of the thermal filamentation instability in generating electromagnetic wave-induced plasma turbulence with a broad spectrum of wavelengths, ranging from meter to kilometer scales. by Joel Cohen. S.B. 43 p. eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Physics. Investigation of thermal filamentation instability over Gakona, Alaska Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="b174f852-ed84-4452-af0e-202924f666f6"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Investigation of thermal filamentation instability over Gakona, Alaska</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2007</PublicationDate> <Authors> <Author> <DisplayName>Cohen, Joel (Joel A.), S.B. Massachusetts Institute of Technology</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Physics.</Keyword> <Abstract>The thermal filamentation instability has been invoked to explain the formation of parallel plate waveguides in mid-latitude ionospheric plasmas during Arecibo, Puerto Rico heating experiments in 1997. The geometry of the kilometer-scale parallel plates predicted by thermal filamentation depends on the mode of the transmitted heater wave, as does the threshold to excite this instability. While plasma heating can excite small-scale irregularities via parametric instabilities, thermal filamentation is thought to produce large-scale irregularities. In Arecibo, the threshold for X-mode to induce irregularities was found to be greater than 1 V/m, while for O-mode it was on the order of mV/m. In recent plasma experiments in high-latitude ionospheric plasmas, carried out at the HAARP facility in Gakona, Alaska in summer 2005, spring 2006, and summer 2006, a weakening in ionogram traces was observed during O-mode and X-mode heating, leading to a scenario detailing the effects of thermal filamentation and short-scale irregularities caused by heating. The Gakona experiments using a high power HF heating facility and multiple diagnostic instruments shed light on the important role of the thermal filamentation instability in generating electromagnetic wave-induced plasma turbulence with a broad spectrum of wavelengths, ranging from meter to kilometer scales.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>