Galileo images of lightning on Jupiter

Citation
B. Little et al., Galileo images of lightning on Jupiter, ICARUS, 142(2), 1999, pp. 306-323
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ICARUS
ISSN journal
0019-1035 → ACNP
Volume
142
Issue
2
Year of publication
1999
Pages
306 - 323
Database
ISI
SICI code
0019-1035(199912)142:2<306:GIOLOJ>2.0.ZU;2-F
Abstract
In October and November of 1997 the Galileo Solid State Imager (SSI) detect ed lightning from 26 storms on the night side of Jupiter, More than half th e surface area of the planet was surveyed. The data include images of light ning against moonlit clouds (illuminated by light from Io) and images of th e 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 similar to 1 500 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 a nd near the centers of westward jets. Latitudes near 50 degrees in both hem ispheres are particularly active, although the northern hemisphere has more lightning overall. The greatest optical energy observed in a single flash was 1.6 x 10(10) J, which is several times larger than terrestrial superbol ts. The average optical power per unit area is 3 x 10(-7) W m(-2), which is close to the terrestrial value. The limited color information is consisten t with line and continuum emission from atomic hydrogen and helium, The int ensity profiles of resolved lightning strikes are bell-shaped, with the hal f-width at half-maximum ranging from similar to 45 to 80 km, We used these widths to infer the depth of the strikes, assuming that the appearance of e ach is the result of light scattering from a point source below the cloud-t ops. We conclude that lightning must be occurring within or below the jovia n water cloud. The occurrence of lightning in regions of cyclonic shear has important implications for the dynamics of Jupiter's atmosphere. (C) 1999 Academic Press.