Nick Mitchell

'Catch a Falling Star - Using Meteors to Study the Winds, Waves and Tides at the Edge of Space'

Every day, about 40 tons of extra-terrestrial material collides with the Earth. This material is mostly in the form of tiny particles originating from comets. At heights of about 100 km, friction heats the particles so that they vaporise, giving rise to the streak of light seen from the ground as a meteor or "shooting star". This meteor region of the atmosphere is, in a very real way, the edge of space.

The meteor region is notoriously difficult to investigate, but hosts a wide range of poorly-understood phenomena. Atmospheric tides and waves launched from below are thought to drive its circulation, coupling together different layers of the atmosphere. Smoke from meteors acts as condensation nuclei for ghostly, polar noctilucent clouds and the meteor region is also home to the giant lightning discharges known as sprites. Its great sensitivity has lead to its being called the miner's canary of climate change.

Professor Mitchell's research involves using sophisticated radars to detect meteors in the atmosphere. The meteors are used as tracers of atmospheric motion and reveal the intricate dynamics of the meteor region. An array of radars at sites ranging from the Arctic to the Antarctic are being used to monitor and investigate this enigmatic part of the atmosphere. The lecture will outline the challenges posed in remote-sensing techniques by meteors and the meteor region, it will present some key recent results, and will look towards future problems.