Optical observations of Saturn lightning by Cassini
Abstract
Visible lightning flashes on Saturn were first detected by Cassini camera during the August 2009 equinox* We review these observations and report new observations of visible lightning in 2009, and in 2010-2011, during the giant lightning storm in the North hemisphere. The 2009 lightning flashes were detected on the night side of Saturn at latitude around 35 degrees South, in a broadband clear filter. The 2011 flashes are detected on the day side in blue wavelengths only. The energies of individual flashes range up to 8x10^9 Joules, larger than the published estimate of 1.7x10^9 Joules, and similar to the strongest lightning on Jupiter and to the strongest terrestrial lightning. The diameter of the of the flashes as seen at the cloud tops is ~200 km. Assuming that light from the lightning diffuses through the clouds above it, lightning occurs 125-250 km. below the cloud tops. Atmospheric levels where water freezes in Saturn clouds are at about these depths. Lightning-generating clouds on the Earth lay at atmospheric levels where water freezes, which means that lightning generation may be similar on Earth and Saturn. We discuss implications of blue-only detections of dayside lightning in 2011 on the lightning spectrum, and simultaneous observations of Saturn lightning in radio wavelengths. *Dyudina, et al., 2010. Detection of visible lightning on Saturn. GRL 37, 9205.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMAE22A..03D
- Keywords:
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- 0319 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud optics;
- 0343 ATMOSPHERIC COMPOSITION AND STRUCTURE / Planetary atmospheres;
- 3324 ATMOSPHERIC PROCESSES / Lightning;
- 5704 PLANETARY SCIENCES: FLUID PLANETS / Atmospheres