| Budget Amount *help |
¥3,360,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
In addition to the traveling atmospheric disturbances (TADs) generated during geomagnetically disturbed periods, we investigated characteristics of the TADs generated during geomagnetically quiet periods. From numerical simulations with a general circulation model (GCM) which covers all the atmospheric regions (troposphere, stratosphere, mesosphere, and thermosphere), we showed TADS generated at around the solar terminator, midnight temperature maximum, and moving auroral oval during geomagnetically quiet periods [Fujiwara and Miyoshi, 2006]. The results suggest that pressure bulges around these areas can generate TADs during the quiet periods.
We also investigated effects of the lower atmosphere on generation and propagation of the TADs. GCM simulations showed that the amplitudes of TADs were largely modulated by the effects from the lower atmosphere, suggesting that variability of TADs was caused by day-to-day variations of the lower atmosphere. The atmospheric gravity waves propagati
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ng from the lower atmosphere should be important as energy and momentum sources in the thermosphere. In order to investigate characteristics of the atmospheric gravity waves in the thermosphere, GCM simulations were performed [Miyoshi and Fujiwara, 20081. The GCM simulations showed that short-period gravity waves were dominant in the thermosphere. The dominant period (zonal phase velocity) of gravity waves decreased (increased) with height.
In this research project, we attempted to estimate the electromagnetic energy deposition rate (Joule heating rate) in the polar cap thermosphere from radar observations which were carried out in collaboration with several countries. From the simultaneous observations with the EISCAT Svalbard radar and the CUTLASS Finland radar, we derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region [Fujiwara et al., 2007]. We will investigate energy budget and dynamics in the polar thermosphere/ionosphere from GCM simulations with use of above radar data. Less
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