Research on the coupling process between the lower thermosphere and the mesosphere in the polar region by using radar observations and model predictions

高纬度地区的低层热层是地球大气中一个独特的区域，因为那里的大气与中低层大气以及电离层和磁层耦合。低层热层受到在其下方传播的大气波及其消散的显著影响。此外，在地磁扰动期间，低层热层通过几个物理过程与电离层和磁层相互作用。然而，这些与上或下区域的耦合过程尚未完全了解。为了更深入地了解这种耦合过程，我们利用EISCAT雷达、其他雷达和模式模拟进行了研究。主要结果如下。(1)利用2003年11月11-19日的EISCAT雷达（KST和ESR）资料，探讨了离子阻力的重要性。我们展示了离子阻力的重要性，并提出压力梯度可能起另一个重要作用。(2)通过对1999年7月1-7日ESR观测资料的分析，探讨了离子阻力对日潮幅值的贡献。我们提出了60%的日潮汐振幅是由离子阻力加速度引起的。(3)我们在2004年12月进行了DELTA火箭运动，以了解菊花活动对低层热层风动力学的影响。通过分析共74小时的FISCAT数据，我们显示了日中潮的逐日变化。(4)基于ESR资料，我们发现来自上、低层的湍流和电磁能量的量级和耗散高度似乎强烈依赖于中性风，特别是在~ 10 km以下。同时，我们导出了1999年3月9日F区高度的热层升温速率高度分布与进入日侧极帽/尖区电磁能量的关联。

The lower thermosphere at high latitudes is a unique region in the earth's atmosphere, because the atmosphere there couples with the middle/lower atmosphere as well as the ionosphere and magnetosphere. The lower thermosphere is significantly influenced by atmospheric waves propagating below as well as by their dissipation. Furthermore, during geomagnetically disturbed periods, the lower thermosphere interacts with the ionosphere and magnetosphere through several physical processes. These coupling processes with upper or lower regions are, however, not yet fully understood. To understand such a coupling process more deeply, we have made studies by using EISCAT radars, other radars and model simulations. Major results are as follows. (1) We investigated the importance of the ion drag by using EISCAT radar(KST and ESR)data obtained for 11-19 November 2003. We showed the importance of the ion drag and also suggested the pressure gradient could play another important role. (2) We investigated the ion drag contribution to the diurnal tidal amplitude by analyzing the data obtained for 1-7 July 1999 by ESR. We presented that sixty percent of the diurnal tidal amplitude arose from the ion drag acceleration. (3)We conducted the DELTA rocket campaign for December 2004 to understand the effect of the anal activity to the lower thermospheric wind dynamics. By analyzing FISCAT data for 74 hours hi total, we showed the day-to-day variability of the sermidiunal tide. (4)We showed that the magnitude and the dissipation height of the turbulent and electromagnetic energy poured from the upper and lower regions seem to be strongly dependent on the neutral wind particularly below〜10 km based on ESR data Also, we derived the height distributions of the thermospheric heating rate at the F region height on 9 March 1999 in association with electromagnetic energy inputs into the dayside polar cap/cusp region.