Trajectory Analysis of Energy and Momentum Transfer in the Upper Thermosphere

Although persistent anomalous features in Earth's upper atmosphere are well-documented, the complex and interconnected physics governing their formation, maintenance, and evolution in the Ionosphere-Thermosphere (IT) region remains poorly understood. For instance, the processes responsible for the formation and development of neutral density cusp enhancements remain unclear, despite various hypotheses from researchers. Although the cusp enhancement is often attributed to Joule heating, the explanation fails to fully account for the density peaks observed by CHAMP measurements. Alternative explanations suggest that energy injections from soft particle precipitation could trigger indirect effects, such as ion upwelling. To complicate things, inertia often creates a delay in the thermospheric response to external energy sources, producing at a first glance what appears to be anomalous behavior when considering only local effects. Furthermore, perturbations in the neutral wind may also play a key role in producing observed, anomalous thermospheric features.
Persistent perturbations of the neutral wind implies spatial wind gradients and largely occur at high latitudes concomitant with neutral density perturbations. Gradients in the neutral wind give way to differing levels of convergence or divergence in localized spots, which consequently produce vertical motion and feedback on the mass and internal energy of the gas. This work seeks to evaluate momentum and energy transfer processes in the high-latitude neutral gas that may create persistent perturbations in neutral gas properties. Utilizing a parcel trajectory analysis in the TIEGCM, energy and momentum deposition processes along a parcel trajectory will be evaluated to understand how the gas evolves while flowing through the high latitude region. Specifically, the delayed response of temperature from an air parcel receiving external energy will be investigated to determine how far “downstream” this deposited energy is transported. Furthermore, momentum transfer processes will be investigated for their efficacy in producing vertical motion via wind divergence. The overall goal of this poster will be to elucidate the influence of non-local effects in the upper thermosphere. Furthermore, it will clarify how these non-local effects can enforce/produce vertical motion, and how to interpret the implications based on the response of thermosphere mass density and wind.