HR: 0800h
AN: SA31A-1105    [Abstracts]
TI: Initial Results Of The Lower Thermospheric Vertical Wind Estimated With Incoherent-Scatter Radars At High Latitudes
AU: * Oyama, S
EM: soyama@gi.alaska.edu
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: bjw4072@mailblocks.com
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive P.O. Box 757320, Fairbanks, AK 99775-7320 United States
AU: Nozawa, S
EM: nozawa@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
AU: Maeda, S
EM: smaeda@kyoto-wu.ac.jp
AF: Kyoto Women's University, 35 Kita-Hiyoshi Imakumano, Higashiyama, Kyoto, 605-8501 Japan
AU: Watermann, J
EM: jfw@dmi.dk
AF: Danish Meteorological Institute, Kastanie Alle 3, Farum, 3520 Denmark
AB: We will present some recent results of the lower thermospheric vertical wind derived with incoherent-scatter (IS) radars at high latitudes. The coupled mesosphere-thermosphere-ionosphere system at high latitudes exhibits complicated temporal and spatial variations in association with the energy coupling between upper and lower regions. While our knowledge of this system has been extended during the last three decades, there remain various interesting phenomena in that region; one of them is the vertical motion in the lower thermosphere (from 90 to 130 km).A limited number of researchers have reported lower thermospheric vertical winds observed with Fabry Perot Interferometer (FPI, 557.7nm) and IS radar. Those results indicate that there is an unexpected level of small-scale structure in the polar thermospheric dynamics often with remarkably large amplitudes. These winds pose various important questions concerning, for example, the momentum transfer in association with atmospheric wave breaking, effects of the thermospheric constituent mixture on chemical reactions, and the energy budget as a part of the magnetosphere-ionosphere-thermosphere coupled system. Our understanding on the lower thermospheric vertical motions is inadequate to consistently explain the experimental data. IS radar data is available to calculate the neutral velocity through the steady state ion momentum equation neglecting ambipolar diffusion. This method has been applied by many other researchers to derive the horizontal component of the neutral wind during the last three decades. However, the conventional IS measurement method should not be applied simply to derivation of the vertical component because the method is subject to significantly large errors, which frequently exceed the calculated vertical neutral speeds. Furthermore, some beam configurations necessarily assume no vertical neutral winds. In this presentation, new radar beam configurations suitable for the vertical neutral wind estimation are introduced, and show some recent results using the new configuration applied to the Sondrestrom IS radar. This method can be applied to the Advanced Modular IS radar (AMISR), which will be planned for Poker Flat, Alaska, in near future. Some features of interest are large vertical shears in the vertical neutral wind below 120 km, and temporal variations with large amplitudes in excess of a few tens m/s.
DE: 2407 Auroral ionosphere (2704)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 1610 Atmosphere (0315, 0325)
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting