HR: 0800h
AN: SA11A-0295    [Abstracts]
TI: UHF and HF Radar Studies of Langmuir Turbulence Experiments at HAARP
AU: * Sheerin, J P
EM: jsheerin@emich.edu
AF: Eastern Michigan Univ., Physics and Astronomy, Ypsilanti, MI 48197, United States
AU: Gerres, J M
EM: jgerres@emich.edu
AF: Eastern Michigan Univ., Physics and Astronomy, Ypsilanti, MI 48197, United States
AU: Bacon, M E
EM: mbacon8@emich.edu
AF: Eastern Michigan Univ., Physics and Astronomy, Ypsilanti, MI 48197, United States
AU: Watkins, B J
EM: ualaska-watkins@usa.net
AF: U. Alaska-Fairbanks, Geophysical Inst., Fairbanks, AK 99775, United States
AU: Bristow, W A
EM: Bill.Bristow@gi.alaska.edu
AF: U. Alaska-Fairbanks, Geophysical Inst., Fairbanks, AK 99775, United States
AU: Turnquist, J E
EM: fsjet@uaf.edu
AF: U. Alaska-Fairbanks, Geophysical Inst., Fairbanks, AK 99775, United States
AU: Oyama, S I
EM: soyama@stelab.nagoya-u.ac.jp
AF: Nagoya Univ., STE Lab, Nagoya, 464-8601, Japan
AU: Heinselman, C J
EM: craig.heinselman@sri.com
AF: SRI, 333 Ravenswood Ave., Menlo Park, CA 94025, United States
AB: High power HF transmitters induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. Radars such as SuperDARN have been used to study artificial field-aligned irregularities (AFAI) created by the high power HF radiowave at the HAARP Ionospheric Observatory, Gakona, AK. A new Modular UHF Ionospheric Radar (MUIR) sited at HAARP, may now be used to monitor changes in the Langmuir plasma waves detected in the UHF backscatter. We report the results from recent campaigns using these new facilities in coordinated and comprehensive studies of strong Langmuir turbulence (SLT). Among the effects observed and studied are: SLT spectra including cascade, collapse, the outshifted plasma line or free-mode, appearance of a short timescale ponderomotive overshoot effect, temporal evolution of SLT, dependence of SLT on growth or suppression of AFAI, dependence of AFAI and MUIR backscatter on HAARP pulselength, duty-cycle, and aspect angle. In particular, we explore the aspect angle effect of increased turbulence with the HF wave directed at small angles to the field line. Langmuir modes parallel to the geomagnetic field are proposed to explain other features in stimulated electromagnetic emissions (SEE). These plasma waves are theorized to play a key role in certain features of radio-induced aurora. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.
DE: 2403 Active experiments
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting