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(1) The mini-barges and S. Tropical Disturbances. 

The JUPOS team (Hans-Joerg Mettig, Michel Jacquesson, Gianluigi Adamoli,
Marco Vedovato) have recently posted their latest set of drift charts.  The
attached chart [-16-26_combined.gif] is a combination of several of these
showing the small dark spots ('mini-barges') at 16-18 deg.S in the fading
SEB(S), along with the tracks of the two S. Tropical Disturbances.

The STrD's have both been prograding in L2, and STrD-1 has been steadily
expanding in longitude: both of these are typical properties of STrD's. (The
f. end of STrD-1 is extremely faint, but is still visible on May 28.)  Both
STrD's have been fading along with the SEB(S), as expected. 

The tiny dark spots in SEB(S) f. the GRS have been retrograding at DL2 ~ +50
deg/month, from March to May.  The HST image on May 11 showed that these are
tiny cyclonic spots, and they are further north than the usual peak of the
retrograding SEBs jet stream, so they probably do not represent the full
speed of the jet.  The JUPOS chart suggests that they passed a larger
cyclonic mini-barge at ~16 deg.S, L2 ~ 170, and this is confirmed by the
attached set of images [Set-f-GRS_Apr0-18_retrospots.jpg].  They did not
merge, although there was some interaction; in fact they may have undergone
a westward acceleration, which might be confirmed by making
higher-resolution JUPOS charts. 

Further f., the chart shows that these spots decelerate as they approach a
larger mini-barge at L2 ~ 220, and apparently they do merge with it.  We
don't have good images showing a merger, but the HST image on May 11 was
taken during one.  The deceleration in some cases happened as the spots
passed STrD-2, consistent with the STrD modulating the SEBs jet, but not in
every case. (They are not deflected southward by the STrD.)

Another mini-barge, passing STrD-1, reversed its drift when alongside the f.
end of the STrD, so it now appears to be trapped within the longitudes of
the STrD.  






(2) The mid-SEB white spot outbreak.

On May 17, Chris Go discovered as new white spot outbreak in the SEB,
starting within the mini-barge at L2=180 (just as a mid-SEB outbreak imaged
by Voyager in 1979 started precisely in the centre of a mini-barge).  This
was surprising as such turbulent activity ceased last autumn, and was not
expected again before the whole cycle of SEB fading is complete. There must
be two opposite tendencies acting in the SEB.  Locally, there is a tendency
for turbulent storms to erupt f. the GRS; but globally, there is a tendency
for the whole SEB to become stabilised with thick cloud cover.  We are still
waiting to see whether this white spot outbreak will lead to a premature SEB
Revival, or will fizzle out allowing the SEB fading to continue.

Unfortunately, southern hemisphere observers have not been able to take
images in the last week, but some images from the northern hemisphere help
to track the outbreak.  Thanks especially to the ALPO-Japan, for posting
some images.  The outbreak has continued to develop, with a bright rift
extending Np., and dark material extending Sf. into STrD-2 (reversing its
recent fading) ? as expected from the currents in this area.  Also a small
dark spot has appeared which may be retrograding past STrD-2. But the
outbreak is still not conspicuous in images of moderate resolution, 10 days
after it started, so it is still possible that it will die away. 

The SED was passing it around May 27. The SED is marked by a brilliant great
white spot (dazzling in Rich Jakiel's image of May 27). This is SED-2, which
has gradually taken over from SED-1 (~30 deg. f. it) as the main complex.  

John H. Rogers,Ph.D.
Jupiter Section Director,
[British Astronomical Association.]

2007年の木星：中間レポート

淡化しているSEBのダイナミクス