HR: 0800h
AN: SA11A-0294    [Abstracts]
TI: Aspect angle dependency of the HF modification measured with MUIR at HAARP
AU: * Oyama, S
EM: soyama@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furo Chikusa, Nagoya, 464- 8601, Japan
AU: * Oyama, S
EM: soyama@stelab.nagoya-u.ac.jp
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive P.O. Box 757320, Fairbanks, AK 99775-7320, United States
AU: Watkins, B J
EM: ualaska-watkins@usa.net
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive P.O. Box 757320, Fairbanks, AK 99775-7320, United States
AB: In this paper we present results of height-resolved observations of F-region Langmuir turbulence measured with MUIR (Modular UHF Ionospheric Radar; 446 MHz) at HAARP (High frequency Active Auroral Research Program) in Alaska, USA. The scientific objective of this paper is to study aspect angle dependency of the HF modification. The best way to achieve the objective is the simultaneous multi-position measurement with the incoherent- scatter (IS) radar. However, general IS radars take, at least, a few seconds to change the radar beam position. MUIR is the best diagnostic tool for this study because it can change the beam direction every IPP (interpulse period) with the phased array system. We conducted two experiments at HAARP; 26 March 2006 and 31 July 2007. For the March 2006 experiment, three MUIR beam positions were selected: geographical vertical, up B (elevation angle = 75 degree), and midway between the two (elevation angle = 82 degree). This experiment was arranged for studying the aspect angle dependency of Langmuir oscillations associated with low HF duty cycle (1%: on/off = 0.1s / 9.9s). The radar-backscatter spectra with 10-ms time resolution were deduced at individual radar-beam positions. For the July 2007 experiment, nine MUIR beam positions around the up B position were selected under relatively high HF duty cycle (50%: on/off = 3min/3min). The presentation will report aspect angle dependencies of (1) the Langmuir oscillation development in the first 100 ms after HF turn-on using data taken during the March 2006 experiment and (2) persistency of the Langmuir oscillation using data taken during the August 2007 experiment.
DE: 2403 Active experiments
DE: 2471 Plasma waves and instabilities (2772)
DE: 6929 Ionospheric physics (1240, 2400)
DE: 6984 Waves in plasma (7867)
DE: 7800 SPACE PLASMA PHYSICS
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting