Author

Nargis Adham

Date Approved

2010

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Physics and Astronomy

Committee Member

James P. Sheerin, PhD, Advisor

Committee Member

James J. Carroll, III, PhD

Committee Member

J. Marshall Thomsen, PhD

Abstract

We report the results from a recent series of campaigns employing the HAARP HF transmitter to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the Super DARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Short pulse, low duty cycle experiments demonstrate control and suppression of artificial field-aligned irregularities (AFAI). This allows the isolation of ponderomotive plasma turbulence effects. Plasma line spectra exhibit a marked dependence on the aspect angle of the HF pump beam and the pointing of the MUIR diagnostic radar. Refraction is shown to play an important role in the observed plasma line spectral density as a function of zenith angle, including the discovery of a second region of strong turbulence displaced southward from the primary HF interaction region along the geomagnetic field line. Background ionospheric conditions are also observed to have a significant effect. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

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