Relative Contribution of Extreme Ultraviolet (EUV) Radiation, Lower Atmosphere Waves, and Geomagnetic Activity on Thermosphere-ionosphere Spatial Structure and Temporal Variability

地球上层大气受到三个外部能量和动量来源的强烈控制：太阳辐射、磁层强迫和向上传播到上层大气的低层大气波。所有这些外部强迫机制都给热层和电离层的结构和动力学带来了相当大的变异性和复杂性。该奖项将研究变化的可能来源，以量化这些基本的外部能量和动量源对热层-电离层系统的相对影响，包括小时至小时和日至日的短时间尺度和短空间尺度。计划开展的模拟工作将加强对低层大气、太阳和地磁强迫驱动的短期变化对T-I系统各种物理过程的影响和相对重要性的理解。这项研究的结果将提出今后在描述中性和电离大气之间的耦合方面有待改进的研究和理论工作领域。这项调查将改善对可能影响各种技术系统的热层-电离层日变化的特征和了解，包括用于商业和军事目的的全球定位系统、导航和高频传播。这些成果将包括对轨道传播模型进行中性密度预测，这些模型用于确定空间物体在相对近期内的位置，以避免碰撞或再入大气层，并对碎片环境作出长期预测。本项目研究的电离层可变性影响全球定位系统和其他用于商业和军事目的的高频无线电系统。这项工作将有助于建立驾驶员-反应关系，这将有助于改进空间气象经验模型或经验/物理混合模型。热层的变化也与航天器的运行有关，因为它们代表了低轨卫星阻力的变化。本研究中使用的模型是CCMC的一部分，因此任何改进都将使其他用户受益，正在使用的代码可供Cedar社区的其他用户使用。

The Earth's upper atmosphere is strongly controlled by three external sources of energy and momentum: solar radiation, magnetospheric forcing, and lower atmospheric waves that propagate upwards into the upper atmosphere. All these external forcing mechanisms introduce considerable variability and complexity into the structure and dynamics of the thermosphere and ionosphere. This award would study the possible sources of the variability to quantify the relative impact of these fundamental external sources of energy and momentum on the thermosphere-ionosphere (T-I) system, for short time scales of hour-to-hour and day-to-day and short spatial scales. The modeling work planned would enhance the understanding of the impact and the relative importance of the short-term variability driven by lower atmosphere, solar and geomagnetic forcing on various physical processes of the T-I system. Results from this study will suggest areas of research and theoretical work for future improvement in the description of the coupling between the neutral and ionized atmosphere. This investigation would improve the characterization and understanding of the thermospheric-ionospheric daily variability that can affect various technological systems, including GPS positioning, navigation and HF propagation for commercial and military purposes. These results achieved would include neutral density predictions for orbit propagation models used to determine the location of space objects in the relatively near-term for purposes of collision avoidance or re-entry predictions, and also to make long-term predictions about the debris environment.This project would support a female scientist (as PI) and an undergraduate student. Ionospheric variability studied in this project impacts GPS and other HF radio systems used for commercial and military purposes. This work would help establish driver-response relationships that would contribute to the improvement of space weather empirical or hybrid empirical/physical models. Thermospheric changes are also relevant to spacecraft operations since they represent variations in LEO satellite drag. The models being used in this study are part of the CCMC, so any improvements will benefit other users, and the codes being used are available to other users in the CEDAR community.