Dynamics of Saturn’s great storm of 2010–2011 from Cassini ISS and RPWS

Sayanagi, Kunio M.; Dyudina, Ulyana A.; Ewald, S. P.; Fischer, G.; Ingersoll, Andrew P.; Kurth, W. S.; Muro, Gabriel; Porco, C. C.; West, Robert A.

doi:10.1016/j.icarus.2012.12.013

Cited by 89 publications

(140 citation statements)

References 66 publications

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“…1. The start and end of this rather atypical SKR behavior coincides roughly with the occurrence of the Great White Spot in Saturn's atmosphere Fischer et al, 2011;Sayanagi et al, 2013), whose temporal occurrence is indicated by the vertical white lines in Fig. 1.…”

Section: Skr and Narrowband Radio Emission Modulation Spectrogramssupporting

confidence: 57%

“…This progressive extension was observed by an increasing longitudinal range of emitted lightning radio emissions and Fig. 9 in Sayanagi et al, 2013), and lightning is known as a good indicator of vertical convection. When the hemispherical deviation of SKR phases and periods started to become large in March 2011, the thunderstorm cells with lightning activity were present over about a quarter of Saturn's circumference at 35 • north extending eastward from the storm's head.…”

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 82%

“…1 to 3. The giant thunderstorm raged at a kronocentric latitude of ∼ 35 • north (all latitudes in this paper are planetocentric), and a convective region of ∼ 10 000 km in latitudinal diameter (called the storm's head) showed a drift of 2.8 • day −1 to the west Fischer et al, 2011;Sayanagi et al, 2013) with respect to the Voyager Saturn Longitude System. This corresponds to a rotation rate of 808 • day −1 or a period of 10.693 h. Thunderclouds in the upper troposphere drifted away with the zonal wind flow creating a turbulent tail which encircled the whole planet within a few weeks after the start of the storm.…”

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 83%

“…shows an image of the main part of the storm taken in early March 2011 by the Cassini camera. Lightning flash rates were extraordinarily high from mid-December to mid-July, indicating violent vertical moist convection, and the main thunderstorm cell was in the GWS head region (Sayanagi et al, 2013), although some lightning was also present in the tail region . The GWS also had a significant influence on the temperature and dynamics of Saturn's stratosphere .…”

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 99%

“…A plot showing the lightning flash rates from mid-June to the end of August 2011 can be found in Fig. 10 of Sayanagi et al (2013). First, the large anticyclonic vortex and the head of the GWS collided in midJune 2011 (Sayanagi et al, 2013;Sánchez-Lavega et al, 2012).…”

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 99%

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A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

Fischer

Groene

et al. 2014

Ann. Geophys.

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Abstract. The periodicity of Saturn kilometric radiation (SKR) varies with time, and its two periods during the first 5 years of the Cassini mission have been attributed to SKR from the northern and southern hemisphere. After Saturn equinox in August 2009, there were long intervals of time (March 2010 to February 2011 and September 2011 to June 2012) with similar northern and southern SKR periods and locked SKR phases. However, from March to August 2011 the SKR periods were split up again, and the phases were unlocked. In this time interval, the southern SKR period slowed down by ~ 0.5% on average, and there was a large jump back to a faster period in August 2011. The northern SKR period speeded up and coalesced again with the southern period in September 2011. We argue that this unusual behavior could be related to the so-called Great White Spot (GWS), a giant thunderstorm that raged in Saturn's atmosphere around that time. For several months in 2011, the visible head of the GWS had the same period of ~ 10.69 h as the main southern SKR modulation signal. The GWS was most likely a source of intense gravity waves that may have caused a global change in Saturn's thermospheric winds via energy and momentum deposition. This would support the theory that Saturn's magnetospheric periodicities are driven by the upper atmosphere. Since the GWS with simultaneous SKR periodicity measurements have only been made once, it is difficult to prove a physical connection between these two phenomena, but we provide plausible mechanisms by which the GWS might modify the SKR periods.

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Section: Skr and Narrowband Radio Emission Modulation Spectrogramssupporting

confidence: 57%

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 82%

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 83%

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 99%

Section: Detailed Behavior Of Skr Modulation During the Gws Eventmentioning

confidence: 99%

See 3 more Smart Citations

A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

Fischer

Groene

et al. 2014

Ann. Geophys.

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Saturn's magnetospheric planetary period oscillations, neutral atmosphere circulation, and thunderstorm activity: Implications, or otherwise, for physical links

Cowley

Provan

2013

JGR Space Physics

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Suggestions that the planetary period oscillations (PPOs) observed in Saturn's magnetosphere may be driven or influenced by neutral atmospheric perturbations motivate an exploratory comparison of PPO rotation periods with available tropospheric and stratospheric determinations. Nonpolar atmospheric rotation periods occupy the range ~10.2–10.7 h associated with the latitudinal jet structure, are similar north and south, and are independent of season, while PPO periods lie in a narrower partly overlapping range ~10.6–10.8 h, are persistently shorter north than south, and undergo a seasonal cycle. In this cycle, widely separated north‐south PPO periods during southern summer converge across equinox to values lying within the atmospheric west jet band, remaining well‐separated from east jet periods. Closest convergence occurred 1 year post equinox, contemporaneously with the switch in seasonal thunderstorm activity from Southern to Northern Hemispheres. Since most large‐scale atmospheric phenomena are related to the west jets, rotating with closely similar periods, they also rotate with periods close to the PPOs under post equinoctial conditions but not otherwise. Specifically, post equinox northern PPOs rotate with a period close to the southern thunderstorms, as well as the north polar spot and hexagon features, while the post equinox southern PPOs rotate with a period close to the pre‐equinox northern “string of pearls” and the first colocated post equinox northern thunderstorm, the Great White Spot event. However, even under these conditions, no consistent correspondences in period are found at a detailed level, which taken together with the lack of correspondence at other times does not suggest a direct physical link exists between these phenomena.

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Dynamics of Saturn's polar regions

et al. 2015

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We analyze data retrieved by the imaging science system onboard the Cassini spacecraft to study the horizontal velocity and vorticity fields of Saturn's polar regions (latitudes 60-90°N in June-December 2013 and 60-90°S in October 2006 and July-December 2008), including the northern region where the hexagonal wave is prominent. With the aid of an automated two-dimensional correlation algorithm we determine two-dimensional maps of zonal and meridional winds and deduce vorticity maps. We extract zonal averages of zonal winds, providing wind profiles that reach latitudes as high as 89.5°in the south and 89.9°in the north. Wind measurements cover the intense polar cyclonic vortices that reach similar peak velocities of 150 m s À1 at ±88.5°. The hexagonal wave lies in the core of an intense eastward jet at planetocentric latitude 75.8°N with motions that become nonzonal at the hexagonal feature. In the south hemisphere the peak of the eastward jet is located at planetocentric latitude 70.4°S. A large anticyclone (the south polar spot, SPS), similar to the north polar spot (NPS) observed at the Voyager times (1980)(1981), has been observed in images from April 2008 to January 2009 in the south polar region at latitude À66.1°close to the eastward jet. The SPS does not apparently excite a wave on the jet. We analyze the stability of the zonal jets, finding potential instabilities at the flanks of the eastward jets around 70°, and we measure the eddy wind components, suggesting momentum transfer from eddy motion to the westward jets closer to the poles.

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Dynamics of Saturn’s great storm of 2010–2011 from Cassini ISS and RPWS

Cited by 89 publications

References 66 publications

A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

Saturn's magnetospheric planetary period oscillations, neutral atmosphere circulation, and thunderstorm activity: Implications, or otherwise, for physical links

Dynamics of Saturn's polar regions

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