Missing Atmospheric Heating from Small-Scale Ionospheric Plasma Variations (MAHSSIV).

The Earth’s upper atmosphere is a dynamic environment comprised of co-existing neutral gases and electrically charged plasma. Various processes affect the density of the more populous neutral atmosphere, including heating through friction as the plasma particles, driven by electrical forces, push past the neutral gas molecules. These electrical forces are linked to the interaction of the Earth’s plasma environment with the Solar wind that flows away from the Sun; a highly variable stream of particles that continuously blows past the Earth. Thus, the heat input to the upper atmosphere varies significantly both in time and location around the planet. The heating of the neutral atmosphere is an important pathway for energy transfer into the wider Earth environment. Understanding the overall heat budget is important for a range of questions in atmospheric science related to changes in the chemistry and dynamics, such as the influence on global atmospheric circulation. An immediate impact of this heating is the consequent atmospheric expansion, which in turn increases the drag on orbiting satellites, affecting satellite lifetimes and collision warning calculations. For example, during the geomagnetic storm in May 2024, the number of orbital manoeuvres for station keeping and collision avoidance increased by a factor of 5 due to rapid and dynamic changes in density. The challenge the science community faces is that methods of tracking this heat input on a scale useful for global calculations rely on large scale observations, these miss the significant input from smaller scale changes in the plasma motion through the neutral gases. Recent studies have shown this missing contribution can double the heating estimated from large scale observations. The aim of this project is to determine where, when and why small-scale heating occurs, thus establishing its overall importance to the upper atmosphere heat budget. We will achieve this through novel use of existing instrumentation and datasets and application of AI techniques followed by dedicated experiments with state-of-the-art instruments coming online in 2025. To capture this small-scale variation on a global scale we will use data from the Super Dual Auroral Radar Network (SuperDARN) which covers both the northern and southern hemispheres from sub-auroral latitudes to the poles. We will derive an empirical relationship between SuperDARN data and small-scale heating through co-located, fine detail auroral and plasma measurements. To enable world-leading impact in our field and beyond we will turn this new understanding into an open-source tool that can be applied to all SuperDARN data, past, present, and future. SuperDARN data is freely available, therefore this tool will have a wide range of beneficiaries, for example: atmospheric modellers (upper atmospheric heating effects influence density, chemistry and circulation patterns), national space weather services providing information to satellite operators trying to predict orbit changes that could lead to collisions in ever more congested space (e.g. the UK Met Office, NOAA space weather prediction service) and space debris tracking teams (e.g. European Space Agency).