Observation and modelling of the upper atmospheric density and winds and their dependence on the geomagnetic conditions

热层的状态及其温度分布受多种因素的影响。这一大气高度现在非常重要，因为所有近地轨道卫星和载人飞船都在这一高度飞行。上层大气的一个特点是部分气体粒子的电离。虽然在过去的几十年里，人们对电离成分进行了深入的研究，但由于缺乏对热层的良好观测，对中性大气的研究受到了很大的影响。在CHAMP卫星发射后，这种情况发生了重大变化。模型一般假定热层结构主要受极紫外太阳通量控制，磁活动应起次要作用。然而，我们最近的测量表明，情况并非如此。在本提案中，我们计划研究电离层-热层耦合对高纬度高层大气动力学的重要性。这项研究将基于CHAMP和EISCAT雷达设施的观测结果。我们关注的是极光区域，在那里大部分的焦耳加热发生。我们的最终目的是表征电离层加热机制，该机制导致热层密度增强并驱动风。还应确定太阳风输入和极紫外太阳辐射的作用。

The state of the thermosphere and its temperature distribution are influenced by many factors. This level of the atmosphere is nowadays of great importance since all satellites in low-Earth orbit and manned spacecraft are flying at these altitudes. A special characteristic of the upper atmosphere is the ionisation of part of its gaseous particles. While the ionised component has been studied intensively during the past decades, the investigation of the neutral atmosphere has suffered greatly due to the lack of good observations in the thermosphere. This has changed significantly after the launch of the CHAMP satellite. It is generally assumed in models that the thermospheric structure is mainly controlled by the EUV solar flux, and the magnetic activity should play a minor role. Our recent measurements, however, indicate that this is not the case. In this proposal we plan to investigate the importance of the ionosphere-thermosphere coupling for the dynamics of the upper atmosphere at high latitudes. The study will be based on observations from CHAMP and the EISCAT radar facilities. We are focusing on the auroral region, where most of the Joule heating occurs. Our final aim is it to characterize the ionospheric heating mechanism which causes thermospheric density enhancements and drives winds. The roles of solar wind input and EUV solar radiation shall also be identified.