Earth’s ionosphere-thermosphere-mesosphere system: The dawn of a new era of exploration
As the so-called “last link” in the electrodynamic chain that connects the Sun to the Earth’s atmosphere, the ionosphere-thermosphere-mesosphere (ITM) system is an important boundary region within the overall system. Despite earnest study and the development of significant understanding over the last century, many features and substantial portions behavior of the ITM system are just now coming to light. Motivated by the desire to understand the physics of the system and how it behaves within the larger Sun-Earth system, as well as the significant space weather effects it has on various space infrastructure, a new era in exploration is now beginning.
After a brief introductory overview of the ITM system, the presentation describes some of the most significant discoveries of the past decade. These discoveries include 1) the profound influences on the ITM system exerted by processes that originate in the lower atmosphere, 2) large plasma enhancements produced during geomagnetic activity, and 3) significant upwelling of neutral gas beneath the Earth’s magnetospheric cusp. These new discoveries and the raft of scientific questions they evoke are used to motivate a spectrum of new investigations. Results from some of the most recent new work are discussed, as are plans for future investigations. These plans are fully consistent with the community-developed research strategy as codified within the National Academies’ Decadal Survey for Solar and Space Physics and include development of missions of various sizes, new instrumentation, and advanced modeling capabilities.