School Colloquia Record

Atmospheric electricity, energetic particles and clouds.

Professor Giles Harrison

Reading University

Fri 23rd Nov 2012
Physics Th C

Not long after Benjamin Franklin’s iconic studies, an atmospheric electric field was discovered in “fair weather” regions, well away from thunderstorms. The fair weather field’s origin was ultimately explained through the global circuit model of the Scottish atmospheric physicist C.T.R. Wilson, who won the Nobel prize for inventing the cloud chamber. In Wilson’s model, charge exchanged by disturbed weather electrifies the ionosphere, and returns via a small vertical current density in fair weather regions. New insights into the relevance of fair weather atmospheric electricity to terrestrial and planetary atmospheres are now emerging through novel instrumentation and measurements, particularly in close relationships between energetic particles, atmospheric electricity, atmospheric aerosol and ions. For example, the atmospheric electric field is highly sensitive to energetic particles, and there is a possible role of the global circuit current density in cloud formation. Beyond natural atmospheric processes, a novel practical application is the use of early atmospheric electrostatic investigations to provide quantitative information on past urban air pollution and visibility.