[2] Jupiter's northern upheavals coming into focus (July 2012.)

2012/13 report no.1:

Jupiter's northern upheavals coming into focus

Observers are now producing images of ever-improving quality as Jupiter moves higher in the morning sky. Attached is a compilation of colour images covering July 3-8, with some key features marked. (I can send an unlabelled version, and a compilation of near-IR images, to anyone who would like them.)  Congratulations to all observers, and also thanks to the ALPO-Japan, from whose web site some of the best images are taken.
The great upheavals on the NTB and NEB are now much better seen.  Revivals of both belts are indeed proceeding dramatically.  The whole region is very complex, with disturbance spanning the NTropZ.

The revived NTB(S) is a striking dark orange belt at most longitudes, although it is still weak from L1 ~ 40-120 (L2 ~ 60-150). (This sector seems to be moving with System I, although its boundaries are too indefinite for actual tracking.)  There is a separate dark grey NTB(N), everywhere except L2 = 60-106, with some darker sectors.

The NTropZ is filled with pale fawn colour plus dark grey spots and streaks. (These are not as distinct as in June so it is not yet clear if they are the same ones.)

The NEB is very complex at all longitudes, pale except for a narrow dark NEB(S), with much internal turbulence.  I can no longer identify any specifically disturbed sector as the source of disturbance.  On the NEBs edge, there are many diverse dark formations. I have numbered them for convenience, but cannot guarantee that these numbers match those used in June, as we have not yet tracked them. A closer study of the most active sector, L1 ~ 260-360, which was passing the most disturbed NEB sector in June, shows rapid changes: some ill-defined blue-grey streaks on NEBs crystallised into a chain of small projections at L1 <~295 (June 27, July 6), while the sector f. them is very disturbed, including bright white spots and very dark blue-grey spots erupting on the NEBs. The unusual brown sector of EZ(N), which enveloped dark features 13-14, disappeared as these spots intruded on it;  but reddish colour has spread from the NEB into the EZ(N) in other sectors, esp. around dark features 5-6.

There is also an orange-brown Eq.Band at most longitudes, with some dark grey streaks in it. This seems to be the most distinct equatorial coloration event since 1989-91, and it could continue to grow.  The source of the reddish material is an outstanding puzzle: e.g., does it condense diffusely, or is it created in vigorous plumes/festoons from the NEBs disturbances?

The southern hemisphere is mercifully normal by contrast.  The SEB has the normal rifting f. the GRS.  The dark S.Trop.Band has now detached from the p. end of the GRS.  The GRS is probably losing its dark S rim as a consequence and thus returning to the normal 'Voyager' aspect, although it is internally pale this year.  In contrast, oval BA (which is approaching the GRS) has reverted to a strong red colour.

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John H. Rogers, Ph.D. Jupiter Section Director,
British Astronomical Association
jhr11@cam.ac.uk
http://www.britastro.org/jupiter/