Date: Thu, 3 Aug 2000 14:35:14 +0100 (BST) From: John Rogers Subject: Re: 2000 Apparition of Jupiter Dear Reta and Mark, Thankyou for your e-mail about observational support for the Cassini flyby. Of course we will be glad to help. Please find attached: (i) A note on how I (for the British Astronomical Association) and other amateurs are now managing observations (2) A brief summary of the 1999/2000 apparition, which is part of an article which should appear in the Journal of the British Astronomical Association this month (2000 August) (3) An interim report on images so far this apparition (4) A compilation of images showing the SEBn/EZ(S) disturbance passing the GRS in 2000 July. Many amateurs worldwide are now taking excellent CCD images; they are being measured using a computer program by our Assistant Directors, Hans-Joerg Mettig and Damian Peach; and the results can be displayed as drift charts in various longitude systems. As there are now many images taken almost every day, it will be most efficient if we send you summaries of observations, at intervals or when you need any particular information. However I am sure the observers will be glad to forward their original images as required. Please let me or others know if particular features are of interest and we can make special efforts to track them. Conversely, we will let you know of any interesting new developments. Best regards, John. ________________________ John Rogers Jupiter Section Director British Astronomical Association &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& BAA Jupiter Section: Report to BAA Council, 2000 [abridged] The transition from 1999 to 2000 has been accompanied by notable changes both on Jupiter and in the Jupiter Section. On the planet, great white ovals that were the longest-lived features apart from the Great Red Spot have come together and merged. In the Section, continuing modernisation of electronic techniques for imaging and analysis has led to a new level of detail and accuracy in our coverage, and to a re-emphasis on the complementary roles of visual observations. There are now three Assistants to the Director of the Jupiter Section: Mike Foulkes, Hans-Joerg Mettig, and Damian Peach. Mike Foulkes is now responsible for analysing visual observations. Hans-Joerg Mettig, who created the JUPOS program that is now used for measuring and analysing images, has done most of the work on that project and prepared the photomosaic maps and longitude charts. Damian Peach, who is both a major CCD contributor and a liaison with the ALPO, has also done some of the image analysis using JUPOS. Observers and recorders worldwide now comprise an informal collaborative network linked by the internet, with the best imagers distributing their images to us and to each other via e-mail or web sites. As a result of the increased number and quality of CCD observers worldwide, and the computer-based analysis of them, our reports can now be complete and satisfactory on the basis of images alone. In future the Section Programme will regard visual and imaging observations as largely complementary. CCD imaging will be the basis of our reports on the nature and movements of features on the planet (as has largely been the case for the past several years). Advanced visual observers will still be welcome to contribute detailed sets of observations that fit into this programme. However, for most visual observers there will be a 'return to our roots', emphasising the value of the visual experience in itself: drawing as an introduction, illustration, and artistic discipline; transit timings as a way of recording unusual spots that may be seen; and colour and intensity estimates. We have also reviewed our nomenclature conventions, and propose that in future longitudes (in Systems I or II) will be abbreviated as L1, L2. Central meridian longitudes will be CM1, CM2, and drift rates will be DL1, DL2. These symbols will make our reports compatible with e-mail. However, in order to maintain the link between our reports and the direct experience and history of visual observers, we will continue to use longitude System II, and we will continue to publish images and drawings with south up. (However for liaison with professional observers we can always produce charts and tables in System III or other longitude systems when required; this is easily done in JUPOS.) The Section's web page < http://www.ast.cam.ac.uk/~baa/jupiter/index.html > provides links to many other web pages maintained by amateur and professional Jupiter observers. John H. Rogers, 2000 July &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& I. Jupiter in 1999/2000: An interim report The 1999/2000 apparition was ideal for observers, with Jupiter at perihelion and north of the equator, and it was also the occasion for interesting events on the planet. The most important of these was the merger of the two remaining South Temperate ovals, which occurred just as the apparition was ending in 2000 March, some 60 years after these well-known landmarks first appeared. North Tropical Region: More conspicuous for visual observers were the many dark features on both sides of the NEB (Fig.1). The NEBn appeared thrown into notable waves at some longitudes; these in fact were the dark 'barges' that formed from 1997 onwards [ref.1], still present, with large bays between them. The adjacent NTropZ was muddied by dusky material that appeared to be flowing flowing off the NEBn and getting caught in small local circulations. One of these formed within a few days in July, at L2 = 205, just p. a dark grey spot on NEBn, where light orange material gathered together to form a 'Little Brown Spot' in NTropZ. However it did not become a true Little Red Spot. From the new year onwards, the dusky material largely disappeared leaving a clearer EZ, though the Little Brown Spot and the barges remained as ever. North Equatorial Region: There was also more dark material than usual on the south side of the NEB, in the NEBs festoons, which led into a massive dark grey Equatorial Band. All this represented a notable change since last apparition; these festoons in northern EZ were much darker and more stable than before. South Equatorial Region: In the southern EZ, and along the SEBn edge, there developed a remarkable and apparently unprecedented 'stormy sector'. It first came to prominence in 1999 November, but developed progressively from 1999 July to 2000 April. The disturbance spread out from a complex at the f. end which often comprised a rift in the SEBn with a dark streak or patch f. it. This complex passed the Great Red Spot on 1999 Aug.18, Oct.15 (Figs.2A, 3), Dec.5 (Fig.4), and 2000 Jan.28 (Fig.2D) and March 28. The f. end complex must be regarded as a great wave, propagating and amplifying in the SEBn jetstream. As a whole it moved more slowly than System I (DL1 ~+1.1 to +1.6 deg/day), but the white rift within it sometimes moved faster (DL1 ~+0.5 deg/day) and was then replaced by a new rift further f. Major dark blue patches developed on its p. side as this sector passed the GRS in October and December, with drifts closer to System I, so they comprised an expanding stormy sector. Other, short-lived spots moved even faster, at DL1 ~ -1 or even -2 deg/day: both white material occasionally spilling Np. from the mouth of the SEBn rift, and chains of tiny spots on SEBn further p. These features were thus running with the SEBn jetstream itself, which was measured at -1.5 to -3.8 deg/day in Voyager images. The f. end complex continued to intensify to the end of the apparition, as shown in the Pic du Midi images in each waveband on 2000 April 7 (Fig.6). Its future fate will be of great interest. South Tropical Region: Although the mid-SEB outbreak of 1998/99 [Refs.1,2] had finished, there was still interesting activity in and around the SEB -- much of it converging on the GRS (Figs.2-4). On the SEBs and STBn, there were outbreaks of jetstream spots, the first for several years. In the SEB f. the GRS, there was the usual 'rifting' activity with white spot outbreaks. This region was targeted by the Galileo spacecraft which showed that the erupting white spots are thunderstorms (see below). After October, this activity diminished, and in March, the SEB seemed more quiet and the GRS redder; however, there was no sign of wholesale fading of the belt. [This is part of a report in press in the JBAA, 2000 August.] &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& JUPITER IN 2000/01 First interim report: 2000 June and July This report is based on CCD images from observers in several countires, especially Tomio Akutsu, Isao Miyazaki, K. Maeda (Japan); Tim Parker, Don Parker, Dave Moore (USA); and Antonio Cidadao (Portugal). General description is based mainly on Miyazaki's colour images all round the planet, 2000 June 21-27 and July 16-21. Analysis and comments are by Damian Peach and Hans-Joerg Mettig as well as myself. SSTB: An interesting feature from last apparition is the faded sector of SSTB seen passing the GRS, possibly be a closed circulation. It has been visible in images since July 1999, and has altered little in size and appearance. STB: The dark DS1, DS2, DS3, all 3 remain from last apparition, up to July 7. Damian's measurements: STB DS#1: 159.2 deg L2 (July 9) and clearly visible on CM on July 16 (Miyazaki image). STB DS#2 (streak): 217.2 deg L2 (July 7). However DS#3 seems to be absent on July 19. Oval BA is still visible, at p. end of a very dark broad sector of STB. (At the f. end is a similar-sized bright white patch; another oval?) Oval BA: positions measured by Hans-Joerg: ------------------------------------------- yyyy mm dd L2 L3 b" Observer ------------- -- -------- ------ ----- 2000 06 21 336.1 263.6 -33.9 (Miyazaki) 2000 06 23 333.9 261.9 -32.4 (Miyazaki) 2000 07 17 326.8 261.2 -33.1 (Miyazaki: Length 12.0 deg.) 2000 07 19 326.9 261.7 -??- (Tim Parker) 2000 07 26 322.5 259.1 -33.1 (CIDADAO; Length 8.3 deg.) 2000 07 28 322.0 259.1 -32.6 (CIDADAO) ------------------------------------------- The motion is still puzzling. It seemed to lie between the former tracks of ovals BE and FA in March, and again in July, but in April and June it was precisely on the former track of BE. We hope that further monitoring will make it clearer. STropZ and GRS: STropZ: Clear and white except near the GRS. GRS: Still a distinct oval in June, with orange colour and a darker S. rim. There was a strikingly dark patch at f. edge of GRS on July 4 and 6 (which I thought might be a transient conjunction of jetstream spots, as in 1999 Nov.) From July 13, there has been a dark S. Tropical Band emerging p. the GRS, from a dark S. rim of the GRS; it seemed to derive from the dark patch f. the GRS. This dark material can be tracked flowing around the S edge of the GRS by comparing Antonio's July 17 images with Isao's July 18 image. GRS centre: L2 = 75.2 (July 13). SEB: SEBs: Fairly quiet, but a few probable SEBs jetstream spots are visible. SEB: A major change is the light yellow SEBZ, first noted in Miyazaki's image on 2000 March 3 p. the GRS, but now all round the SEB. However the SEB(S) is still very dark and a similar SEBZ was present in 1995, so there is no indication of general fading. Some SEBZ disturbance does persist f. the GRS though Isao and Damian regard it as pale and inactive. It has grey filaments in contrast to the light yellow SEBZ everywhere else. Southern equatorial region: Continuing the major disturbance that developed during the last apparition, SEB(N) and EZ(S) are now disturbed all round the planet, with blue shadings and streaks in EZ(S), though still most striking p. the main complex, as in March. The main complex was still very striking in June (L1 ~ 175), with brilliant white 'GWS/rift' and dark blue patch as in March-April; as Hans-Joerg's chart shows, this has maintained exactly the same slow drift since January. The interruption of the EB alongside the dark blue patch at the f. end had become even more prominent; in June it was a large white spot lying across the equator. The sector leading up to the main complex was passing the GRS in mid-July, and the images were very striking. Cidadao's (July 17) showed the disturbance p. the main complex, very spectacular as it passed the GRS. Akutsu's (July 16) and Miyazaki's (July 18) showed the main complex approaching the GRS, in methane as well as in colour. There was the usual very bright patch on July 16 but it had closed up by July 18; however on both dates, the methane images showed the main complex was methane-dark with an obvious 'step-up' f. it, as seen in the Pic du Midi images on 2000 April 7 and Miyazaki's images on June 25. Ditto July 23 (Akutsu), with the main complex passing GRS. Akutsu also takes near-IR continuum images (820 nm, I-band, july 31), which show the bluish patches in EZ(S) very dark but the SEB(N) virtually absent, even a long way from the main complex. Northern equatorial region: EZ(N) is dull, and EB is still broad and dark. Both EB and dfestoons are even broader than last apparition, diffuse and grey. Lighter areas of EZ(N) are creamy [Damian says "Note the faint orange colouration to the EZ(N)."] The NEBs projections are large and dark. North Tropical region: NEB: Extensive rifting. NEBn/NTropZ: Still barges and bays, and some dusky streaks in NTropZ. In June these app. included the former Little Brown Spot at L2 ~ 160 but in July it is barely visible. Some streaks connect NEBn to NTBs displaying the shear across the zone. This activity seems to have developed so that from L2 ~ 240-330, NEB is broadened to the N, both in June and July. We may indeed be seeing a very long-drawn-out NEB broadening event. There has been interest in the colour of the NTropZ since the last colour image in 2000 April showed a yellowish tint. Such a tint has been seen on a few images (mostly lower resolution) but depends on processing. It is still unclear whether yellow colour is an artefact of low resolution, or whether white colour is an artefact of image-processing. In most images, NTropZ appears white. NTB: Still a very dark massive belt. There are no conspicuous NTBs jetstream spots, but little humps may be the ones that have been tracked for 3 years. ******************************************************************* *******************************************************************