DRivers and Impacts of Ionospheric Variability with EISCAT-3D (DRIIVE)

One of the biggest unanswered questions in the solar-terrestrial science that underpins Space Weather research is:

How does the high latitude ionosphere vary on small scales in response to driving from above and below?

An immediate practical follow-on question would be: what are the impacts of small-scale processes to the larger upper atmosphere environment? The answers to these questions are essential for understanding how Space Weather impacts on society. This area is of growing importance to the UK, as evidenced by recent investment in operational Space Weather forecasting at the Met Office and the inclusion of Space Weather in the National Risk Register.

To answer these questions, we need to understand the processes that occur in the region known as the Mesosphere-Lower Thermosphere-Ionosphere (MLTI - 75-200 km altitude) and how they affect the wider coupled ionosphere-upper-atmosphere system. The ionosphere and upper neutral atmosphere are intrinsically linked: perturb one and the other changes. This has implications for our near-Earth space environment where variations in atmospheric density produce changes in the orbits of space debris, increasing the risk of unforeseen collisions; a significant natural hazard as Geospace grows more crowded. Space Weather plays a big role in modifying this region through frictional Joule heating and particle energy deposition but is not the only important driver. The weather in the lower atmosphere drives changes in the ionosphere that can be comparable to external forcing, but the relative contribution is far from understood, as the processes are under-observed. Another barrier to knowing that contribution is our inability to properly account for small scale variability, whether driven from above or below. Upper atmosphere models typically do not resolve this variability, yet we know that not doing so leads to underestimates of the magnitude of atmospheric heating by as much as 40%. This heating is a process that relies both on space weather driving and changes in the neutral atmosphere composition and dynamics.

This project will use the brand new, next generation ionospheric radar: EISCAT-3D, located in northern Fennoscandia. This is part funded by NERC. It is capable of imaging a large volume of the local ionosphere and providing measurements on horizontal scales of 1-100 km. It will be unique with high vertical and temporal resolution and multipoint measurements of the ionospheric electric field vector. The field of view of the radar will cover a decent proportion of the auroral zone in latitude, such that results from the measurements made there can be applied to the wider region.

We will use the unique capabilities of the radar to quantify the energy that is deposited into the MLTI from space weather events and also measure the impact of small-scale waves that propagate upwards from the lower atmosphere. We will use a range of support instrumentation, including newly deployed optics, and determine how the coupling between the neutral and ionized regimes affect the energy balance. Resolving these processes will let us establish their role in upper atmospheric heating.

We will use the E3D observations together with comprehensive upper atmosphere models to determine and apply methods of correcting estimates of heating due to the small-scale changes. Using advanced models with inputs informed by the results of our observations we will determine how the small-scales affect the low altitude satellite debris field in the Earth's outer environment.

This Project directly addresses two of the priority areas (and touches on others) that have been identified in the NERC Highlight Topic Announcement of Opportunity, and so answers the key question: How does the high latitude ionosphere vary on small scales in response to driving from above and below?