Dyudina, U.A., Ingersoll, A. P., Ewald, S. P., Porco, C.C., Kurth, W. S., Fischer, G., West, R. A. (2010). "Detection of Visible Lightning on Saturn" American Astronomical Society, DPS meeting #42, #41.04.


Abstract
Until now, evidence for lightning on Saturn has been indirect - through radio emissions and cloud morphology. Here we report the first visible detection of lightning (Dyudina et al., 2010), on the night side on August 17, 2009 at -36.4 degrees +/- 0.1 degrees planetocentric latitude and 10.6 degrees +/- 0.9 degrees west longitude. No other locations produced lightning detectable by either imaging or radio. This is the same latitude band on the planet that the imaging team has called `storm alley' for the last 6 years: i.e., where we observe all of the major storms that are believed to produce lightning because of the radio emissions and cloud morphology. The lightning images are consistent with a single cloud flashing once per minute. The visible energy of a single flash is comparable to that on Earth and Jupiter, and ranges up to 1.7 X 10^9 Joules. The diameter of the lightning flashes is -200 km, which suggests the lightning is 125-250 km below cloud tops. This depth is above the base of the liquid H2O-NH3 cloud and may be either in the NH4SH cloud or in the H2O ice cloud. Saturn's lower internal heat transport and likely 5-10 fold enrichment of water largely explain the lower occurrence rate of moist convection on Saturn relative to Jupiter.

Dyudina, U. A., A. P. Ingersoll, S. P. Ewald, C. C. Porco, G. Fischer, W. S. Kurth, and R. A. West (2010), Detection of visible lightning on Saturn, Geophys. Res. Lett., 37L09205