Excitation of Langmuir wave turbulence in high-frequency (HF) pump waves over Gakona, Alaska
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214283034-MIT.pdf
Description
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Checksum (MD5)
996cc3754c870fd73c3b5a03d8dbfb30
Author(s)
Rokusek, Daniel L
Advisor(s)
Min-Chang Lee.
Date Issued
2007
Publisher
Massachusetts Institute of Technology
Abstract
(cont.) Investigated in this thesis are the excitation and observation of Langmuir wave turbulence caused by the parametric decay instability (PDI) in high-frequency space plasma heating experiments conducted at the NSF/DoD High Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska during the spring and summer of 2006. The PDI is the decay of an electromagnetic (EM) wave into an electron plasma wave (i.e., Langmuir wave) and an ion acoustic wave. When the excited Langmuir wave parametrically decays into another Langmuir and ion acoustic wave pair, a cascade of Langmuir waves can occur provided that the instability threshold is satisfied. According to recently advanced theory by Kuo and Lee [2005], there are two possible methods of cascade: non-resonant and resonant. While the non-resonant cascade proceeds at the location of excitation, the resonant process occurs at lower altitudes to minimize losses that the non-resonant process incurs by remaining at the excitation altitude. Such losses are caused by the frequency mismatch effect, as the decay ion acoustic wave frequency becomes much less than that of the normal ion acoustic waves. In their downward propagation the Langmuir waves in the resonant cascade suffer from propagation losses, however these losses are less than those associated with the non-resonant process. The resonant process is therefore expected to have a lower threshold. Theoretical claims and calculations are compared to observations made at Arecibo, Puerto Rico and Tromso, Norway. Claims are also are supported by incoherent backscatter radar observations made at the HAARP facility in Gakona.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2007.
Includes bibliographical references (p. 53).
Subjects
Nuclear Science and Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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