[15] The SEB revival outbreak Nov 1st - Dec 3rd, 2010.

SEB Revival - NOVEMBER 21st - 27th.

Attached is a third compilation of images showing the continuing development of the SEB Revival from Nov.21-27.  Many thanks to all the imagers, whether included here or not.  Thanks too to Tomio Akutsu for the compilation of his own multi-spectral images, which provide an excellent hi-res overview of the whole Revival so far.

In the last week, there have been no new brilliant plumes at the original source, but more bright storms developing several degrees preceding it, and I think these comprise an expanding storm system that has evolved from the very first bright plume (WS1), including the bright plume that then appeared just north of it (WS-N).

On Nov.20, WS4 had appeared (L2=291), in a southerly streamer remaining from WS1.  On Nov.23, there was renewed brightening within WS-N (visible and methane-band).  This turned out to be a new spot, named WS5 (L2= 286), which became very bright on Nov.24 and drifted south, separating from WS-N which is prograding.

I think that WS-N, WS4, and WS5, are all storms within a single expanding complex, derived from WS1; and that this bright storm complex, together with the very dark oblique streak along its f. edge, now defines the p. edge of the central branch of the Revival, which should be prograding. (The leading edge of the central branch in previous Revivals has often been marked by a bright white spot.) 
The last white spot that appeared at the source itself was WS3, which persists, though by Nov.23 it was small in visible light and faint in methane. WS3 brightened again on Nov.26 (L2 = 294, still).

Meanwhile a fine chain of dark spots is retrogading on SEB(S).

Clear and steady skies!

Best wishes,

John Rogers.

SEB Revival expanding (2010 Nov.27 to Dec.3)


The SEB Revival is now proceeding vigorously in classical style, and all three 'branches' are becoming distinct.  Attached is a fourth compilation of images of the SEB Revival, covering Nov.27 to Dec.3.  New bright spots, also bright in methane images, appeared on  Nov.29 (WS6, L2=280, in the leading edge complex) and Dec.1 (WS7, L2=298, at the original source).  So far, all the bright spots have appeared in these two locations.  A diagram of the outbreak is given at the bottom of the compilation.


Details of the major branches of the Revival during this period:

1) Source: WS7 was first imaged in visible light on Dec.1 (but on Nov.30 in infrared images by Dr Glenn Orton et al.). (NB: I referred to this as WS6 in earlier messages to some observers - apologies for any confusion.)     WS3 had moved north; it was still very methane-bright up to Dec.1; but then it became entrained and distorted as it approached the SEBn jet and began prograding rapidly.

2) Central branch:  A distinct 'leading edge complex' has formed, derived from the original plume (WS1) and 'dark column'. The latter is now an oblique dark streak, and on its p. side is an extended bright area derived from WS1, in which other bright (and methane-bright) plumes have repeatedly arisen: WS-N, WS4, WS5, and now WS6.  The motion of the central branch is still rather slow: DL2 = -10 deg/month (DL3 = -2 deg/month) for WS1, WS-N, and WS3, according to JUPOS measurements just produced by Michel Jacquesson.    WS5 had drifted south and so was slower-moving than the rest, and was still weakly methane-bright, up to Dec.1.  WS6 appeared just p. it on Nov.29, much more methane-bright.  Then WS6 moved south while WS5 moved north in a cyclonic swirl (Dec.1-3).  There have been other, smaller and shorter-lived, bright spots in the same latitude from Nov.27 onwards. On Dec.3, as observers have pointed out, the expanding disturbance is filling in with dark brown material. This may be the first sign of return of a 'normal' SEB region.


3) Northern branch:  From Nov.29 onwards, the 'leading edge complex' began extending very rapidly at its Np. end.  The old WS-N elongated and was surrounded by a large dark loop, comprising the original dark grey column on its Nf. side, a blue (and very methane-dark) streak on its Sp. side, and a dark greenish-grey streak on its N side. The latter streak has the same mysterious greenish-grey tint as the rest of the SEB(N), but is much darker, and is now elongating rapidly in the p. direction as a reviving segment of SEB(N). So this may be the emergence of the northern branch.


4) Southern branch:
There is now an impressive series of retrograding dark spots on SEB(S).  I can send an additional compilation of images if wanted, aligned to track some of these spots.  Speeds have not yet been measured, but some provisional results emerge from inspection of the images.  There are key questions about how these spots form: in particular, what is their relation to the pre-existing 'sawtooth' or wave pattern on the SEBs, and is there any sign of vortices forming?

The sawtooth pattern is still clearly present p. and f. the Revival region, and some observers have commented that the dark material seems to be filling up the pre-existing projections.  This seems to have been the case for the earliest spots, up to Nov.19 (although even then the pattern was not entirely stable as it passed the outbreak). There is still a trio of projections at the leading (western) end of the chain that appear to have been darkened in this manner. But then, another very dark spot emerged Sf. the source on Nov.19-21, and became the leading end of a sinuous dark SEB(S) which broke up into a chain of dark spots.  These are larger, and more widely spaced, than the pre-existing projections (spacing 7-10 deg. for these dark spots, 6 deg. for the sawtooth pattern).  By Nov.29, in addition, white spots from WS4 etc. have been disrupting the flow of the sawtooth pattern past the outbreak.  So it appears that the larger dark spots replace the sawtooth pattern, in the same latitude (21 deg.S). However they still seem to be formed by dark material filling spaces around bright spots, and there is complex, variable substructure. They have not yet formed distinct vortices. This is still expected to happen in the coming days.    So, as of Dec.1, the retrograding chain begins with three darkened pre-existing projections at its western end, followed by four larger dark spots, followed by more chaotic dark material still emerging from the outbreak source region. Although they change shape rapidly, all these spots have maintained their identities since soon after they emerged.

Best wishes,

John