Major outbreak on NTBs jet-stream (2011/12 report no.6) |
Jupiter reappears with major outbreaks on NEB and NTB(: 2012/13 report no.1) by John H.Rogers
In the last week of the 2011/12 apparition, a major new outbreak started on the largely-faded North Temperate Belt (NTB). We have been expecting such an outbreak this year, as explained at: http://www.britastro.org/jupiter/2010report19.htm --based on the recent acceleration of the jet back to super-fast speeds at cloud-top level, and the 5-year periodicity of such outbreaks from 1970 to 1990. (The last such outbreak was in 2007.) The following alert was sent out (2012 April 25): gManos Kardasis has just sent the attached images, from April 19, noting the very dark spot on the NTBs, with a bright spot preceding it. This is very likely a new outbreak on the super-fast NTBs jet-stream! Confirmation is urgently needed! There was nothing there in his image of this longitude on April 12, nor in the few other images that I have seen from recent weeks (by H. Einaga and L. Zielke). Obviously Jupiter is now too close to the Sun for good-quality imaging but if anyone can get any images of these longitudes, even in daylight, or can send images from recent days, please do so....h If on the super-fast jet, the bright spot should move with DL1 ~ -5 deg/day (DL3 ~ -13 deg/day), while the dark streak would elongate behind it and become turbulent, as observed in 1990 and 2007. From the size of the dark streak, it probably began about a week before the first observation. On 2012 April 19, 17:19 UT, the bright spot was at L1 =75 (L3 = 336), followed by a very dark streak from L1 = 79 to 99. On April 21, 18:39 UT, Gianluigi Adamoli fortuitously managed to record these features: probable bright spot at L1 ~ 64, dark streak from L1 = 70 to 91, consistent with the expected drifts. There were no further images of the longitude of the bright spot, but images on April 26 (by Manos Kardasis and John Rozakis and Antonio Lasala) recorded the f. end of a very dark segment at L1 ~ 90. No further useful images were obtained after that date, in spite of observersf efforts, as the planet went behind the Sun. All the data indicate that a typical super-fast outbreak had begun, but it was frustratingly impossible to determine accurate speeds or to resolve the features. It is therefore vitally important to get images as soon as possible after solar conjunction. It may be possible to confirm the outbreak by obtaining drift rates for residual spots, and/or by finding a revived NTB(S), initially turbulent and turning orange. These are typical sequels of the super-fast outbreak that are not recorded in any other circumstances. Great credit is due to the observers, especially Manos Kardasis, for persevering under such difficult circumstances and discovering this important event, which could so easily have been missed. Attachment: Images of the start of the NTBs outbreak, 2012 April. John Rogers 2012 June. 2012/13 report no.1: Jupiter reappears with major outbreaks on NEB and NTB John Rogers (BAA), 2012 June 27 Just before Jupiter disappeared behind the Sun, two very important disturbances erupted in the North Equatorial Belt and North Temperate Belt. Both belts had faded (lightened) during 2011, and were very quiet. The NEB was exceptionally narrow and its south edge devoid of major features, a state not seen since about a century ago. The NEB outbreak [ref.1] began on March 8 when a bright eriftf appeared and started to generate very dark, slow-moving formations on the NEBs edge. It seemed possible that this would be the start of a new NEB broadening event (last seen in 2009), and perhaps of a fully-fledged eNEB Revivalf such as used to happen a century ago. The NTB outbreak [ref.2] was first detected on April 19 with a very bright and very dark spot on the NTBs edge. It seemed likely that this was the start of a new NTBs jet-stream outbreak (last seen in 2007). Both events would be spectacular, and important for establishing the long-term patterns of activity in Jupiterfs atmosphere, so it was frustrating that Jupiter then disappeared behind the Sun. So we eagerly awaited the new apparition to find out how the phenomena developed. Manos Kardasis in Greece, having discovered the NTBs outbreak in some of the very last images of the last apparition, also made the first image of the new apparition on June 4, which confirmed that both outbreaks had developed impressively. He has posted a map made from his near-infrared (IR) images on June 4-9 [refs.3,4]. Other observers have also made great efforts to get images, in daylight or at low altitude, and although many of the images inevitably have poor resolution and quality, they are invaluable for revealing the progress of these spectacular and rapidly-evolving disturbances. These images provide strong evidence that a NTBs super-fast outbreak has indeed occurred, and that a NEB Revival is probably underway. There are striking dark spots in NTropZ and on NEBs, and reddish or ochre colour appears to cover much of the NEB, NTropZ, and NTB(S). Compilations of the images from 2012 June 13-24:
Fig. 1. Set of colour images, arranged by L2. The resolution is inevitably low, and therefore the colours should be interpreted with caution; low resolution, esp. in blue light, can cause reddish colour to spread from belts to zones. Apparent colours also vary depending on the selectivity of the blue filter used, and depending on the processing. South is up.
Fig.2. Set of IR or red-light images, arranged by L2, with major features indicated by colour-coded arrows. These images give better resolution, and show the dark grey spots clearly, but they fail to show the extensive reddish areas, so RGB images are also needed. (Also compare with Kardasisf earlier map [ref.3].)
Fig.3. Set of the same images, arranged by L1, with major dark formations on NEBs indicated by numbers (and one very bright spot arrowed). The numbering is tentative (and has a break in a poorly-observed sector); these identifications need to be checked by measuring longitudes.
Fig.4. Previous maps of the NEB and NTB for comparison. (a) NEB Revival on 1893 Oct.19-20, possibly similar to its state in mid-June, 2012. (b) NTB outbreak on 2007 April 3, similar to its state when first observed on 2012 April 19. (c) NTB Revival on 2007 May 21-22, similar to its state in mid-June, 2012. (Further captions and credits are on the images.) Fig.5. Set of methane-band images (890 nm), all by Tomio Akutsu (Philippines). South is up. The NEB and NTB are less affected by the fading and revival in methane band than in visible light, probably because the high-altitude haze (which is seen bright in methane images) is determined more by the fixed flow of the jet-streams than by the local meteorology. However I am surprised that there is not more dimming in methane in the highly turbulent sector of the NEB (where convective plumes might be methane-bright), and in the reddish sector of the NTB (where the reddish colour might itself be a high-altitude haze, as in 2007). The visibly dark spots in NTropZ are methane-dark. > Tentative descriptions and interpretations: NTZ: This is broad and white. Perhaps the NNTB has whitened as compensation for the darkening of the NTB? NTB: The NTB(S) has revived as a dark orange-brown belt around most of the circumference. This colour is typical after a super-fast outbreak. From L2 ~ 210-310, it has not yet revived but comprises dark and bright spots - probably the tail end of the super-fast outbreak, though we have still not been able to measure any drift rates. (See comparison map in 2007 May, at a similar time after the start of the outbreak, which matches the present state well.) Also from L2 ~ 210-310, a separate dark grey NTB(N) is visible; it may also be present elsewhere though narrower. (In IR images, only this N component is visible.) NTropZ: This zone has an ochre tint in many images - less so in Akutsufs, perhaps because he has higher resolution or a different filter set. The colour may vary with longitude but it certainly varies with the observer. Future images should show whether the colour has really diffused across the NTropZ from the outbreaks, or whether it only appears to do so due to low resolution (which might also apply to historical obsfns). Anyway, this tint has been recorded in some previous years, probably always associated with a NTBs outbreak and/or a NEB Revival [ref.5]. It is particularly reminiscent of 1985, another year when a strong reddish colour in the NTropZ gave evidence that the NTB had undergone a super-fast outbreak during solar conjunction, maintaining a 5-year periodicity. There are four very dark grey spots, roughly stationary at L2 = 109, 219, 274, and 359 (a long bar) (all arrowed in the image set). These are very unusual for the NTropZ, as it is anticyclonic, but similar spots have been seen during previous NEB broadenings or revivals. (One example is in the comparison map from 1893.) The very dark spot at L2=277 has persisted from June 6-24, but the one at L2=109 (June 9-18) had N and S components on June 19 (Peach, hi-res) which had sheared apart on June 20 (Go, hi-res). So these spots may not be long-lived. NEB: The appearance is bizarre, but entirely consistent with an on-going NEB Revival, as shown in the map from 1893 (adapted from [ref.5].) The most remarkable sector is from L2 ~ 50-130, which is very pale, but happened to be captured in hi-res images on July 19-20 by Peach, Go, & Akutsu, which showed it to be filled with complex light spots and streaks. I suspect that this is an intensely convective eriftedf region comprising the source of the outbreak. As sketched on the 1893 map, it would be generating dark material f. it on the NEBn (possibly retrograding?), and intensifying the dark blue-grey eprojectionsf on the NEBs prograding past it. At most other longitudes, IR images show only the narrow NEB(S). The northern half of the belt is pale and ochre-coloured, possibly not yet much changed by the outbreak. The IR images in Fig.3 show the NEBs eprojectionsf. Typical dark grey or bluish-grey NEBs formations are seen at most longitudes, moving approx. with System I (L1). Some are very intense, and may be the same very dark ones that were seen to appear at the start of the outbreak. I suspect that these are a series generated as the NEBs flowed past the rifted region, as we saw commencing in March. The leading projections have now spread all around the planet, while the trailing ones (nos.10 & 11) are still being formed. EZ: NEBs projections nos.13-14 are embedded in a rare brown sector of EZ(N), ~25 deg. long. There is also a broad brownish Eq. Band at some longitudes, perhaps indicating the onset of a coloration event, as in 2006-07. The EZ(S) is still white. SEB: The SEB is generally normal, with a typical rifted region f. the GRS, and dark orange-brown colour over a large part of the belt. One unusual feature is the cream-coloured spot at L2 = 101, which has been present there since autumn, 2011, but seems to be bigger and brighter now. Its nature is a mystery. STropZ: The GRS is at L2 = 180. It still has a dark ring around it, and a dark grey S.Trop.Band p. it, as in 2011. Oval BA is approaching the GRS from the f. side, and shows a trace of red colour even in these lo-res colour images. ------------------------------- References to our previous bulletins:  Report no.5. The NEBs outbreak in 2012 March. (2012 April) http://alpo-j.asahikawa-med.ac.jp/kk12/j120409r.htm [Further images, analysed by G. Adamoli, show that large dark NEBs formations persisted up to the last useful image on April 25; the leading one maintained its unusual drift of DL1 = +58 deg/month.]  Urgent alert for Jupiter observers: Outbreak on NTB. (2012 April 25) [This original alert was e-mailed and posted on PVOL & Report no.6. Major outbreak on NTBs jetstream (2012 June) [An updated version being posted along with the present report.]  Jupiter Map, 4-9 June 2012, by Kardasis. http://alpo-j.asahikawa-med.ac.jp/kk12/j120609r.htm  Alert: Major outbreaks occurring on Jupiter. (2012 June 12) http://alpo-j.asahikawa-med.ac.jp/kk12/j120612r.htm  Rogers JH (1995), 'The Giant Planet Jupiter', Chapter 8 (Cambridge University Press, 1995). ________________________________________________________________ John H. Rogers, Ph.D. Jupiter Section Director, British Astronomical Association
http://www.britastro.org/jupiter/ [British Astronomical Association.]
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