Solar activity and dynamics of the mesosphere and lower thermosphere

中间层和低层热层（MLT）区域在大气中从50公里延伸到150公里。它受到来自上方的太阳UV/EUV辐射和高能粒子的沉淀，以及来自下方的大气波的影响。因此，MLT区域是耦合进入大气的太阳能和由大气波和潮汐输送到热层/电离层的能量的界面。向上传播的重力波最终在那里破裂并消散。这样，它们在MLT中的动量通量辐散不仅驱动了平均经向环流，也影响了热结构。反过来，这种动力反馈影响了MLT的纬向风结构，并影响了大气低层产生的向上传播波的过滤条件。MLT区域的能量收支是复杂的，包括UV/EUV光谱范围内N2、O2、O和O3的太阳辐射加热，CO2和NO的红外辐射冷却，放热化学反应的化学加热，电离层电流的焦耳加热以及动力驱动。这些项中的大多数直接或通过化学动力学反馈受到太阳短期变率的影响。本项目将利用高分辨率高顶化学-气候模式UA-ICON-MECCA，分析太阳短期变率（太阳EUV耀斑、地磁风暴和太阳质子事件）对MLT区域组成、能量平衡、重力波传播和耗散、温度和环流的影响。有了这个详细的分析，我们将有助于填补理解我们的大气和空间之间的过渡区域的能量收支的缺失部分。

The mesosphere and lower thermosphere (MLT) region extends from 50 to 150 km in the atmosphere. It is affected from above by solar UV/EUV irradiances and precipitating energetic particles, as well as by atmospheric waves from below. So, the MLT region is an interface to couple solar energy into the atmosphere and the energy transported by atmospheric waves and tides into the thermosphere/ionosphere. Upward propagating gravity waves eventually break and dissipate there. In this way, their momentum flux divergence in the MLT drives the mean meridional circulation but also impacts the thermal structure. In turn, this dynamical feedback affects the zonal wind structure of the MLT and influences the filtering conditions for upward propagating waves generated in the lower part of the atmosphere. The energy budget of the MLT region is complex, being comprised of solar radiative heating by N2, O2, O, and O3 in the UV/EUV spectral range and IR radiative cooling by CO2 and NO, chemical heating by exothermic chemical reactions, and Joule heating of the ionospheric currents, as well as dynamical drivers. Most of these terms are affected by short-term solar variability, either directly or through chemical-dynamical feedbacks. In the proposed project, we will analyze the influence of short-term solar variability – solar EUV flares, geomagnetic storms and solar proton events – on the composition, energy budget, gravity wave propagation and dissipation, temperature, and circulation of the MLT region based on dedicated model experiments with the high-resolution high-top chemistry-climate model UA-ICON-MECCA. With this detailed analysis, we will help fill in a missing piece in understanding the energy budget of the transition region between our atmosphere and space.