The lower thermosphere-ionosphere (LTI) system is the transition region between Earth’s atmosphere and space. It is characterized by large changes in the dynamics, energetics, composition, and ionization of the atmosphere. In this region, the atmosphere transitions from a well-mixed to a diffusively separated state, and the atmosphere becomes increasingly ionized. Meanwhile, the electrodynamic wind dynamo couples different regions across latitudes and altitudes.
The spatial-temporal morphology of the LTI is influenced by forcing from the lower atmosphere and solar and geomagnetic activity. Their interplay leads to complex regional and global variability on timescales from hours to months, creating a challenge for understanding the LTI behavior. Although a basic understanding of the connection between the lower and upper atmosphere via waves and global circulation changes has been achieved, we still have a limited understanding of the LTI structure itself, e.g., spatial-temporal structure and variability of neutral and plasma density, composition, temperature, and wind, as well as the processes determining them, and their relative importance.
This limited understanding is partly due to the fact that we lack continuous and high-resolution observations in the LTI region. Consequently, LTI processes were often investigated indirectly with data taken remotely from ground or at Low-Earth-Orbit (LEO) altitudes (> 300 km). However, Very LEO (VLEO) altitudes (< 300 km) are increasingly becoming important for modern space-based infrastructure, and therefore there is a growing need to better understand the variability of the VLEO environment and the processes controlling the region, including but not limited to neutral and plasma composition, wind, and temperature, and electrodynamics.
This session invites presentations that define the critical environmental knowledge needs at VLEO altitudes. We equally solicit studies that quantify LTI structure, variability, and driving processes using numerical, statistical and machine learning models and current observations, including uncertainty quantification, as well as new observing techniques or proposed mission concepts.