磁暴期间，中低纬日侧电离层的等离子体在增强的对流电场的作用下被输运至极区，并形成舌状电离（Tongue of Ionization，TOI）现象。受观测手段的覆盖范围和模式精度所限，目前磁暴期间TOI结构影响热层的过程和机制尚不清楚。本项目计划利用高精度磁层-电离层-热层耦合模式研究暴时极区电离层热层系统的响应，重点围绕TOI结构对热层的影响为主题，分析TOI结构对热层温度、密度和风场等参量的影响过程，探究其影响的大小、空间范围、时间尺度，及对太阳风/行星际磁场和季节等条件的依赖性，甄别焦耳加热、摩擦加热等因素在热层变化中的相对贡献，揭示暴时极区电离层-热层耦合的物理机制，为提高空间天气预报能力服务。

During geomagnetic storms, the energy from the solar wind can be deposited into the polar I-T system and induce complex variations. The ionospheric plasma in the polar cap region often flows as a two-cell convection pattern during geomagnetic disturbances. The high-latitude enhanced convection electric field during storm time transports the dense plasma from the daytime mid-latitudes into the polar cap region and then causes a tongue of ionization (TOI), which is characterized by a longitudinally narrow region of enhanced plasma density from middle to high latitudes in the noon-midnight direction. In this study, we use the high-resolution Coupled Magnetosphere-Ionosphere-Thermosphere Model (CMIT) to study the behavior of polar thermosphere during geomagnetic storms. We will concentrate on the TOI effect on the thermospheric temperature, density, and winds, including the magnitude, latitudinal and longitudinal range, time scale and the solar wind/interplanetary magnetic field dependence of the influences. The underlying physical mechanisms such as the processes of Joule heating, collision heating, and ion drag will also be investigated. This study will improve the accuracy and reliability of spacecraft navigation and positioning, and give better forecasts of space weather.