The Great Saturn Storm of 2010-2011

TL;DR

The paper details the 2010-2011 Great Saturn Storm, a rare planetary-scale atmospheric event observed by Cassini and telescopes, revealing its dynamics, lightning activity, and atmospheric effects.

Contribution

It provides a comprehensive analysis of the 2010-2011 Saturn storm using multi-instrument data, highlighting its unique features and atmospheric impact.

Findings

Storm affected latitude band 25-48°N

Detected significant lightning activity

Indicated substantial energy release comparable to Saturn's radiated power

Abstract

In December 2010, a major storm erupted in Saturn's northern hemisphere near 37 degree planetographic latitude. This rather surprising event, occurring at an unexpected latitude and time, is the sixth "Great White Spot" (GWS) storm observed over the last century and a half. Such GWS events are planetary-scale atmospheric phenomena that dramatically change the typically bland appearance of the planet. Occurring while the Cassini mission was on-orbit at Saturn, the Great Storm of 2010-2011 was well-suited for intense scrutiny by the suite of sophisticated instruments onboard the Cassini spacecraft as well by modern instrumentation on ground-based telescopes and onboard the Hubble Space Telescope. This GWS erupted on December 5th and generated a major dynamical disturbance that affected the whole latitude band from 25 deg to 48 deg N. Lightning events were prominent and detected as outbursts and flashes at both optical and radio wavelengths. The activity of the head ceased after about seven months, leaving the cloud structure and ambient winds perturbed. The tops of the optically dense clouds of the storm's head reached the 300 mbar altitude level where a mixture of ices was detected. The energetics of the frequency and power of lightning, as well as the estimated power generated by the latent heat released in the water-based convection, both indicate that the power released for the storm was a significant fraction of Saturn's total radiated power. The effects of the storm propagated into the stratosphere forming two warm airmasses at the 0.5-5 mbar pressure level altitude. Related to the stratospheric disturbance, hydrocarbon composition excesses were found. The decades-long interval between storms is probably related to the insolation cycle and the long radiative time constant of Saturn's atmosphere, and several theories for temporarily storing energy have been proposed.