Numerical simulations of generation and propagation of the traveling atmospheric disturbances in the thermosphere

除了地磁扰动期产生的旅行大气扰动（TADs）外，我们还研究了地磁平静期产生的旅行大气扰动的特征。通过一个覆盖所有大气区域（对流层、平流层、中间层和热层）的一般环流模式（GCM）的数值模拟，我们展示了在地磁安静期，在太阳终止点、午夜最高温度和移动极光椭圆附近产生的TADS [Fujiwara和Miyoshi， 2006]。结果表明，这些区域周围的压力凸起可以在安静时期产生TADs。我们还研究了低层大气对TADs产生和传播的影响。GCM模拟表明，TADs的振幅在很大程度上受到低层大气的影响，这表明TADs的变化是由低层大气的逐日变化引起的。来自低层大气的更多的重力波作为热层的能量和动量源应该是重要的。为了研究热层大气重力波的特征，进行了GCM模拟[Miyoshi and Fujiwara， 20081]。GCM模拟表明，短周期重力波在热层中占主导地位。重力波的主导周期（纬向相速度）随高度减小（增大）。在这个研究项目中，我们试图通过与几个国家合作进行的雷达观测来估计极地帽热层中的电磁能量沉积速率（焦耳加热速率）。通过EISCAT斯瓦尔巴雷达和CUTLASS芬兰雷达的同时观测，我们得到了F区高度的热层升温速率高度分布与进入昼侧极帽/尖区的电磁能量相关[Fujiwara et al., 2007]。我们将利用上述雷达数据从GCM模拟中研究极地热层/电离层的能量收支和动力学。少

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 … More 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