Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsa12a0672o&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SA12A-0672
Physics
0310 Airglow And Aurora, 0358 Thermosphere: Energy Deposition, 2427 Ionosphere/Atmosphere Interactions (0335), 3369 Thermospheric Dynamics (0358)
Scientific paper
Various magnetospheric processes strongly dominate the dynamics and the composition of the polar thermosphere, modifying the wind and temperature structures generated by solar heating alone. Energetic particles precipitating from the magnetosphere along geomagnetic field lines cause ionization at ionospheric heights. Because acceleration of neutral wind above about 125 km by ion drag is proportional to ion density and is rather insensitive to neutral density, the neutral winds can be driven into the ionospheric convection in the precipitating area, even in the E-region. The combination of the ion convection and high energetic particle precipitation provides a momentum source by ion drag and a heat source by Joule and particle heating processes. Effects of the auroral activity on thermospheric motions have been studied widely using optical and radio techniques and theoretical calculations. While the general circulation models show relatively good agreements with observations, those models do not always provide a reality of small-scale structures at polar thermosphere and ionosphere both in the electric field and in the plasma density associated with fine structures of the auroral arc. To understand thermospheric responses to fine structures in the energy input originated in the magnetosphere needs further comparison of thermospheric winds obtained from high-resolution models and from observations. In this paper, thermospheric winds observed with the Fabry-Perot interferometers (FPIs, λ = 630.0 nm) at Poker Flat, Alaska (65.11° N, 147.42° W) are compared with winds predicted with a high-resolution two-dimensional nonhydrostatic compressible thermospheric model. To provide realistic inputs for the model calculation, we estimated auroral heated region using data from the meridian-scanning photometer at Poker Flat and the VHF radar at Anchorage, Alaska. Comparison of the model calculations with observed data show that the combination of the horizontal background-winds and spatial and temporal variations in electromagnetic energies affect vertical wind structures significantly in the vicinity of the heated region. Even in the core of the heated region, vertical winds show downward motions in F-region heights in association with wavelike structures, which may result in gravity waves.
Conde Maria M.
Ishii Makoto
Oyama Satoshi
Shinagawa Hiroyuki
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