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Published December 1999 | public
Journal Article

Galileo Images of Lightning on Jupiter

Abstract

In October and November of 1997 the Galileo Solid State Imager (SSI) detected lightning from 26 storms on the night side of Jupiter. More than half the surface area of the planet was surveyed. The data include images of lightning against moonlit clouds (illuminated by light from Io) and images of the same storm on the day and night sides. The spatial resolution ranged from 23 to 134 km per pixel, while the storms ranged in size up to ∼1500 km. Most storms were imaged more than once, and they typically exhibit many flashes per minute. The storms occur only in areas of cyclonic shear and near the centers of westward jets. Latitudes near 50° in both hemispheres are particularly active, although the northern hemisphere has more lightning overall. The greatest optical energy observed in a single flash was 1.6×10^(10) J, which is several times larger than terrestrial superbolts. The average optical power per unit area is 3× 10^(−7) W m^(−2), which is close to the terrestrial value. The limited color information is consistent with line and continuum emission from atomic hydrogen and helium. The intensity profiles of resolved lightning strikes are bell-shaped, with the half-width at half-maximum ranging from ∼45 to 80 km. We used these widths to infer the depth of the strikes, assuming that the appearance of each is the result of light scattering from a point source below the cloudtops. We conclude that lightning must be occurring within or below the jovian water cloud. The occurrence of lightning in regions of cyclonic shear has important implications for the dynamics of Jupiter's atmosphere.

Additional Information

© 1999 by Academic Press. Received February 11, 1999; revised July 29, 1999. We thank Don Banfield, Peter Gierasch, Mike Belton, Ken Klaasen, Amy Simon, Sarah Milkovich, and Shawn Ewald for various valuable contributions. This work was supported by the Galileo Project, NASA, and NSERC of Canada (B.L.).

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023