First bulletin of the 2003/04 Jupiter apparition (2003 Oct.20):

Here is a brief summary of notable features seen on images of Jupiter so far this apparition, with particular attention to the SEB. Reviewing your recent images, it is evident that there are actually two SEB features which I had not clearly distinguished before: the f. end of a mid-SEB outbreak at L2 ~ 192, and the p. end of a dark reddish spot at L2 ~ 246. All longitude measurements below are in System II and were made approximately on my screen; accurate JUPOS measurements will no doubt follow.  In addition to images sent to us directly, I have looked at images by Iga and Einaga, kindly provided on the ALPO-Japan web site.

The dark reddish spot lies in a moderately broad SEBZ, centred at L2 = 249 (Oct.10 & 15), L2 = 252 (Oct.18).  This is presumably a cyclonic barge (more common in the NEB), in a generally quiet region.  It is shown well in images by Sanchez (Oct.10), Sanchez and Peach (Oct.15), and Ng and Hatton (Oct.18).

The mid-SEB outbreak had begun during solar conjunction, and was discovered visually by Horikawa (Sep.17; f. end L2 ~ 192). This is the first distinct mid-SEB outbreak since 1998, although there have been annual outbreaks closer to the post-GRS disturbance which were not so distinctly separate. It consists of a very broad SEBZ, which would probably be turbulent if viewed at hi-res.  Its f. end was shown clearly in images by Hatton (Sep.21), Peach (Oct.10), and Einaga and Ng (Oct.18) – always at L2 = 191-194.  However it is possible that, as usual with such events, it consists of a source region where bright white spots arise repeatedly and prograde at 1-2 deg/day.  The Oct.18 images show a very bright pair of white spots at the f. end of the active SEBZ, which were probably new.  When discovered, the turbulent bright SEBZ of the mid-SEB outbreak had already merged with the perennial turbulence f. the GRS, as shown by Horikawa (Sep.26, visual), Iga and Einaga (Oct. 8, images via ALPO-Japan), and Hatton (Oct.12). Therefore it had begun before mid-September, but after June 1-3, as it was not shown in images then by Jason Hatton, Don Parker, and Dave Moore.

Multispectral images by Colville (Oct.13) show a remarkable aspect to the mid-SEB outbreak. There is a sharp discontinuity at L2 ~ 162, which appears to be the f.end of the bright spots in visible and I-band, but the f.end of a very dark SEB in the methane band – as though the turbulent SEBZ is very dark in methane. The appearance is reminiscent of the South Equatorial Disturbance in 2000-2001, although this may be misleading.  I suspect that the sector L2 ~ 162-192 also contained bright spots which were not clearly resolved in visible light but were bright in methane.   These images were of low resolution, with the planet still low, so it will be interesting to obtain further methane images of these longitudes as soon as possible, before the mid-SEB outbreak ceases.

Meanwhile the GRS is unusually reddish.  This was first indicated by lo-res images by Iga (Sep.26) and Jacquesson (Sep.27) and confirmed by much better images by Iga and Einaga (Oct.8) and Hatton (Oct.12). Its longitude of L2=89 is not significantly different from the pre-conjunction average of L2=88 in 2003 May.

Images showing the mid-SEB outbreak also show two long-lived anticyclonic white ovals near the same longitude: Oval BA on the STB (L2 = 223, Sep.21; 212, Oct.18), and white spot Z on the NEBn (a bright bay at L2 ~ 202).  As Damian pointed out, white spot Z is still at the f.end of long-lived barge B1; they have remained a stable pair for a year.

John Rogers, 2003 Oct.20

Jupiter Section Director,

British Astronomical Association.

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PS: To those who provide images:

Thankyou to those of you who have adopted the recommended format for images (south up) and filenames (2003Oct20_Name).  To those who haven’t, our recommendations are copied below.  Even if you have principled objections to using these exact formats, I do urge you at least to give the date in the order year-month-day, as 6-figure random numbers are very confusing!