Jupiter’s South Temperate domain: Behaviour of long-lived features and jets, 2001-2012
John Rogers , Gianluigi Adamoli, Grischa Hahn, Michel Jacquesson, Marco Vedovato, & Hans-Jörg Mettig
(JUPOS team and British Astronomical Association)
Summary
This report gives an overview of Jupiter’s South Temperate domain, covering the years 2001-2012, from amateur images and the JUPOS database. We summarise the long-term history of the major features, principally a succession of structured cyclonic sectors in the South Temperate Belt (STB), one of which is associated with the single large anticyclonic oval (oval BA); and the STBn jet that is associated with them. Informative comparisons can be made between the speed-vs-latitude relationship for individual spot(s), which we here define as the Zonal Drift Profile (ZDP), and the speed-vs-latitude relationship for the smallest cloud features, which is the Zonal Wind Profile (ZWP). We provide a synthesis which explains most of the previously puzzling features of this domain.
The STB consists of alternating structured and undisturbed sectors, and we track the origin and fate of the structured segments over the years. At the preceding end of one of them is oval BA, the only large anticyclonic oval in the domain. The other structured sectors consist of cyclonic regions, which begin as small dark spots or streaks remote from oval BA, then expand, and eventually catch up with the dark segment following BA, inducing intense disturbance in and around it. This cycle has been completed three times in 15 years.
Oval BA has been reddish since 2006. It sometimes undergoes large changes of drift rate, which appear to be caused by two factors: the cyclic impacts and shrinkages of structured STB segments impinging on its following side, and the periodic passages past the Great Red Spot. From 2008 onwards it has been shrinking in length and probably in width, which accounts for a progressive southwards shift in its zonal drift profile [speed-vs-latitude relationship]. The same evolution was shown by the three earlier long-lived ovals.
The retrograde STBs jet and the prograde STBn jet are both shown to vary with longitude and time. The ZDP for dark spots in the STBs jet and STZ varies with longitude (in relation to the ‘STB Remnant’) and with time, suggesting that the ZWP also varies. Spacecraft data show that the STBs jet is often faster in structured sectors; so is one component of the STBn jet.
The STBn jet, as observed by spacecraft, has two sub-peaks at ~26ºS and 29ºS. We show that the 29ºS subpeak is relatively stronger alongside STB dark segments, and that the speeds of these sub-peaks also vary with time. The STBn jet often carries small dark spots, emanating from long-lived dark STB segments, and we show that they tend to drift northwards during their lives, probably from one sub-peak to the other. These results reveal a novel longitudinal and latitudinal structure in a prograde jet.
The report in full can be downloaded via the
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5) Figure legends and miniatures
John
Rogers,
2013
July 16th
John H. Rogers, Ph.D. Jupiter Section Director,
British Astronomical Association
jhr11@cam.ac.uk
http://www.britastro.org/jupiter/