Electrical processes take place in all planetary atmospheres. There is
evidence for lightning on Venus, Jupiter, Saturn, Uranus and Neptune, it
is possible on Mars and Titan, and cosmic rays ionise every atmosphere,
leading to charged droplets and particles. Controversy surrounds the
role of atmospheric electricity in physical climate processes on Earth;
here, a comparative approach is employed to review the role of
electrification in the atmospheres of other planets and their moons.
This book reviews the theory, and, where available, measurements, of
planetary atmospheric electricity, taken to include ion production and
ion-aerosol interactions. The conditions necessary for a global
atmospheric electric circuit similar to Earth's, and the likelihood of
meeting these conditions in other planetary atmospheres, are briefly
discussed. Atmospheric electrification is more important at planets
receiving little solar radiation, increasing the relative significance
of electrical forces. Nucleation onto atmospheric ions has been
predicted to affect the evolution and lifetime of haze layers on Titan,
Neptune and Triton. For planets closer to Earth, heating from solar
radiation dominates atmospheric circulations. Mars may have a global
circuit analogous to the terrestrial model, but based on electrical
discharges from dust storms, and Titan may have a similar global
circuit, based on transfer of charged raindrops. There is an increasing
need for direct measurements of planetary atmospheric electrification,
in particular on Mars, to assess the risk for future unmanned and manned
missions. Theoretical understanding could be increased by
cross-disciplinary work to modify and update models and
parameterisations initially developed for a specific atmosphere, to make
them more broadly applicable to other planetary atmospheres. The
possibility of electrical processes in the atmospheres of exoplanets is
also discussed.
