Monte Carlo Radiative Transfer Modeling of Lightning Observed in Galileo Images of Jupiter

Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter

“…Without identifying the cloud base, water cloud observations cannot constrain the deep water abundances. Dyudina et al (2002) analyzed the optical power of lightning detected in the H α line in Galileo SSI images finding that the lower power observed is consistent with lightning generated at p > 5 bar. Lightning production at such great depths implies a supersolar water abundance.…”

“…Lightning production at such great depths implies a supersolar water abundance. Although observations of water ice at the visible cloud tops and lightning on Jupiter (Smith et al, 1979;Borucki et al, 1982;Little et al, 1999;Dyudina et al, 2002) indicate the presence of convective water clouds, the observations are consistent with relatively rare, localized convective events. Observed lightning events are limited to regions of the planet with cyclonic shear, and near the centers of westward jets (Little et al, 1999).…”

Dynamical implications of Jupiter's tropospheric ammonia abundance

“…These thunderstorms are probably driven by condensation of water, as ammonia and H 2 S are too scarce to drive thunderstorm-strength updrafts or cause cloud electrification (Gierasch and Conrath, 1985;Gibbard et al, 1995;Yair et al, 1995). The lightning occurs at altitudes ∼ 80-120 km below the ammonia clouds, at pressures of 5-10 bars (Borucki and Williams, 1986;Little et al, 1999;Dyudina et al, 2002), consistent with the water-condensation pressure of ∼ 6 bars. Furthermore, portions of the thunderstorm cloud tops have pressures exceeding 4 bars, where the only condensate is water (Banfield et al, 1998;Gierasch et al, 2000).…”

Lightning on Jupiter observed in the line by the Cassini imaging science subsystem

“…This steadysource approach is good to first order for long (tens of seconds) exposures because the storms are flashing approximately every 5 s (Little et al, 1999;Dyudina et al, 2002). However, 21 out of 53 Galileo lightning spots have short exposures (6.4, 8.5, or 12.8 s).…”

“…However, even on Earth with its conductive ground producing the effect of a "mirror" charge below the cloud and thus stimulating cloud-to-ground lightning, two thirds of the lightning occurs within the clouds and does not reach the ground. In the absence of the conductive surface all jovian lightning is likely to occur within the clouds (see discussion in Dyudina et al (2002)). To support clouds at the depths of more than 5 bars and the corresponding temperatures, water abundance in the deep jovian atmosphere should be more than 1 × solar.…”