The bottom-up approach

Imagine trying to understand the weather across our entire planet if you only had a handful of weather balloons: it would be impossible. This is just like the problem facing scientists studying the Earth’s magnetosphere. At any one time, there are only a dozen or so scientific satellites probing the relevant environment. These give a detailed picture of what is going on at a few specific locations, but the gaps between the measurements are huge, usually tens of thousand of kilometres.

British researchers are at the forefront of ground-based investigations into the Earth’s ionosphere and magnetosphere. These can be built and operated reliably for a tiny fraction of the cost of satellites. Measurements of the ionosphere made by instruments on terra-firma can be mapped out thousands of kilometres into the magnetosphere to reveal the structure and motion of near-Earth space.

The Space Plasma Exploration by Active Radar (SPEAR) facility, recently built on Spitsbergen in the Arctic archipelago of Svalbard by the University of Leicester, is a state-of-the art experiment. Not only can it be used as a radar, tracking the motion of plasma flows in the Earth’s ionosphere, it can beam high power radio waves into the sky in order to heat the ionosphere. This mimics natural effects and can be used to probe the physical processes at play in the upper atmosphere.

Also located on Svalbard is one of the European Incoherent Scatter (EISCAT) radars: a project funded in part by the UK to with British efforts coordinated by the Rutherford Appleton Laboratory. Enormous radar dishes at this site and others in Norway, Sweden and Finland can measure the motion, composition, temperature and density of the cocktail of electrically charged particles that make up the ionosphere. Meanwhile, devices called riometers continually listen to the cosmic radio noise coming from the sky. These faint signals are absorbed by increased numbers of electrons arriving from space. By monitoring their the absorption of the cosmic noise background using the British-built IRIS and ARIES riometers in northern Scandinavia, scientists at Lancaster University are learning about the showers of electrically charged particles that rain into the upper atmosphere.

As well as being success stories in their own right, many UK instruments are part of an international family of experiments looking at the nature of our planet’s space environment. The British Antarctic Survey and the University of Leicester both operate radar systems designed to measure the motion of the atmosphere between about 100-200 km altitude. The Co-operative UK Twin Located Auroral Sounding System (CUTLASS) is made up of two radars located in Finland and Scandinavia, both operated by the University of Leicester, while the BAS’s radar is located at Halley Base in Antarctica. All three radars form part of the international SuperDARN network – a unique project that links 18 radars in the polar regions of both the northern and southern hemispheres. By sharing data with their international colleagues, UK scientists are using the gigantic SuperDARN network to investigate ionospheric plasma at the edge of space and investigate processes deep within the magnetosphere.