Plasma-neutral interactions in the lower thermosphere-ionosphere: The need for in situ measurements to address focused questions

• Published in: Frontiers in astronomy and space sciences Vol. 9
• Main Authors: Sarris, Theodoros, Palmroth, Minna, Aikio, Anita, Buchert, Stephan Christoph, Clemmons, James, Clilverd, Mark, Dandouras, Iannis, Doornbos, Eelco, Goodwin, Lindsay Victoria, Grandin, Maxime, Heelis, Roderick, Ivchenko, Nickolay, Moretto-Jørgensen, Therese, Kervalishvili, Guram, Knudsen, David, Liu, Han-Li, Lu, Gang, Malaspina, David M., Marghitu, Octav, Maute, Astrid, Miloch, Wojciech J., Olsen, Nils, Pfaff, Robert, Stolle, Claudia, Talaat, Elsayed, Thayer, Jeffrey, Tourgaidis, Stelios, Verronen, Pekka T., Yamauchi, Masatoshi
• Format: Journal Article
• Language: English
• Published: Frontiers Media 30-01-2023; Frontiers Media S.A
• Subjects: altitudes below 200 km; altitudes below 200 km; atmosphere space transition region; decadal survey; in situ measurements; ion neutral coupling; lower thermosphere ionosphere; LTi; plasma neutral interactions; Sciences of the Universe; LTi; ion neutral coupling; atmosphere space transition region; plasma neutral interactions; altitudes below 200 km; lower thermosphere ionosphere; in situ measurements; decadal survey
• ISSN: 2296-987X; 2296-987X
• DOI: 10.3389/fspas.2022.1063190

The lower thermosphere-ionosphere (LTI) is a key transition region between Earth’s atmosphere and space. Interactions between ions and neutrals maximize within the LTI and in particular at altitudes from 100 to 200 km, which is the least visited region of the near-Earth environment. The lack of
in situ
co-temporal and co-spatial measurements of all relevant parameters and their elusiveness to most remote-sensing methods means that the complex interactions between its neutral and charged constituents remain poorly characterized to this date. This lack of measurements, together with the ambiguity in the quantification of key processes in the 100–200 km altitude range affect current modeling efforts to expand atmospheric models upward to include the LTI and limit current space weather prediction capabilities. We present focused questions in the LTI that are related to the complex interactions between its neutral and charged constituents. These questions concern core physical processes that govern the energetics, dynamics, and chemistry of the LTI and need to be addressed as fundamental and long-standing questions in this critically unexplored boundary region. We also outline the range of
in situ
measurements that are needed to unambiguously quantify key LTI processes within this region, and present elements of an
in situ
concept based on past proposed mission concepts.