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

Sayanagi, Kunio M. and Dyudina, Ulyana A. and Ewald, Shawn P. and Fischer, Georg and Ingersoll, Andrew P. and Kurth, William S. and Muro, Gabriel D. and Porco, Carolyn C. and West, Robert A. (2013) Dynamics of Saturn’s great storm of 2010–2011 from Cassini ISS and RPWS. Icarus, 223 (1). pp. 460-478. ISSN 0019-1035. doi:10.1016/j.icarus.2012.12.013. https://resolver.caltech.edu/CaltechAUTHORS:20130412-074051508

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Abstract

Saturn’s quasi-periodic planet-encircling storms are the largest convecting cumulus outbursts in the Solar System. The last eruption was in 1990 (Sánchez-Lavega, A. [1994]. Chaos 4, 341–353). A new eruption started in December 2010 and presented the first-ever opportunity to observe such episodic storms from a spacecraft in orbit around Saturn (Fischer, G. et al. [2011]. Nature 475, 75–77; Sánchez-Lavega, A. et al. [2011]. Nature 475, 71–74; Fletcher, L.N. et al. [2011]. Science 332, 1413). Here, we analyze images acquired with the Cassini Imaging Science Subsystem (ISS), which captured the storm’s birth, evolution, and demise. In studying the end of the convective activity, we also analyze the Saturn Electrostatic Discharge (SED) signals detected by the Radio and Plasma Wave Science (RPWS) instrument. The storm’s initial position coincided with that of a previously known feature called the String of Pearls (SoPs) at 33°N planetocentric latitude. Intense cumulus convection at the westernmost point of the storm formed a particularly bright “head” that drifted at −26.9 ± 0.8 m s^(−1) (negative denotes westward motion). On January 11, 2011, the size of the head was 9200 km and up to 34,000 km in the north–south and east–west dimensions, respectively. RPWS measurements show that the longitudinal extent of the lightning source expanded with the storm’s growth. The storm spawned the largest tropospheric vortex ever seen on Saturn. On January 11, 2011, the anticyclone was sized 11,000 km by 12,000 km in the north–south and east–west directions, respectively. Between January and September 2011, the vortex drifted at an average speed of −8.4 m s^(−1). We detect anticyclonic circulation in the new vortex. The vortex’s size gradually decreased after its formation, and its central latitude shifted to the north. The storm’s head moved westward and encountered the new anticyclone from the east in June 2011. After the head–vortex collision, the RPWS instrument detected that the SED activities became intermittent and declined over ∼40 days until the signals became undetectable in early August. In late August, the SED radio signals resurged for 9 days. The storm left a vast dark area between 32°N and 38°N latitudes, surrounded by a highly disturbed region that resembles the mid-latitudes of Jupiter. Using ISS images, we also made cloud-tracking wind measurements that reveal differences in the cloud-level zonal wind profiles before and after the storm.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.icarus.2012.12.013DOIArticle
https://arxiv.org/abs/1607.07246arXivDiscussion Paper
ORCID:
AuthorORCID
Sayanagi, Kunio M.0000-0001-8729-0992
Ewald, Shawn P.0000-0002-1567-9154
Fischer, Georg0000-0002-0431-2381
Ingersoll, Andrew P.0000-0002-2035-9198
West, Robert A.0000-0002-4320-2599
Additional Information:© 2012 Elsevier Inc. Received 13 April 2012. Revised 14 December 2012. Accepted 17 December 2012. Available online 10 January 2013. Our work was supported by the Cassini-Huygens mission, a cooperative project of NASA, ESA, ASI, managed by JPL, a division of the California Institute of Technology, under a contract with NASA. The authors thank the two anonymous reviewers for their very constructive comments. G.F. was supported by a grant from the Austrian Science Fund (FWF project P24325-N16) and by a short-term scholarship at the University of Iowa.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
FWF Der WissenschaftsfondsP24325-N16
University of IowaUNSPECIFIED
Subject Keywords:Saturn, Atmosphere; Atmospheres, Dynamics; Meteorology
Issue or Number:1
DOI:10.1016/j.icarus.2012.12.013
Record Number:CaltechAUTHORS:20130412-074051508
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130412-074051508
Official Citation:Kunio M. Sayanagi, Ulyana A. Dyudina, Shawn P. Ewald, Georg Fischer, Andrew P. Ingersoll, William S. Kurth, Gabriel D. Muro, Carolyn C. Porco, Robert A. West, Dynamics of Saturn’s great storm of 2010–2011 from Cassini ISS and RPWS, Icarus, Volume 223, Issue 1, March 2013, Pages 460-478, ISSN 0019-1035, 10.1016/j.icarus.2012.12.013. (http://www.sciencedirect.com/science/article/pii/S0019103512005192)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37894
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 Apr 2013 15:04
Last Modified:09 Nov 2021 23:32

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