February 1, 1999

BAA report from John Rogers, tracking info and ALPO alerts from John McAnally, new IJW lab discipline info from Julie Moses, images from Don Parker.


John H. Rogers (
British Astronomical Association

1999 January 5

This message includes a second interim report on the 1998 apparition, based on images up to Nov.23. As it was completed, further images were received from Isao Miyazaki up to Dec.26, which show three features that deserve immediate attention. [Longitudes are System II. Images by Damian Peach (UK), Paolo Tanga (Italy), Don Parker (USA), Bratislav Curcic & Stefan Buda (Australia), have also helped to track these spots.]

  1. Ovals BE and FA in the S. Temperate region are closer together. They were centred about 38 deg. apart until mid-October, but then converged in November, and were only about 30 deg. apart in December. Although this distance is still much greater than between BC and DE before they merged, and does not appear to be diminishing further at present, there is still the possibility of further convergence.
  2. A new bright white spot has appeared on SEBs p. the GRS. It was first imaged on Oct.28 (absent on Oct.14), and on Nov.4 it was at L2 = 22, moving with DL2 = +6 deg/mth, towards the GRS which was at L2 = 68. There is no reason to regard this spot as unusual, but it is interesting because it is bright, and because it is on the former track of a STropZ dark spot that temporarily formed the p. end of the S. Tropical Band.
  3. The largest NEBn 'barge' is being impacted by a more rapidly moving NEBn/NTropZ white 'bay' ('spot Z'). These spots both date from 1997, and have been interacting since 1998 October; see the following report for details. As the white bay pressed against the f. end of the barge in November, the bay deepened and slowed to DL2 = -5 deg/mth, while the barge was deformed and then faded. Meanwhile a new dark barge formed f. the bay, stationary at L2 = 352. Images from Nov.16 to Dec.5 even suggest that very dark material may have flowed from the old barge to the new barge around the south edge of the bay! On Dec.12 the white bay Z was still very deep, at L2 = 336.


[This report is based on images by Isao Miyazaki up to 1998 Oct.24, and a smaller number of images by Don Parker up to Nov.23. Latitudes are zenographic; some were measured by Hans-Joerg Mettig and Andre Nikolai from images by various observers. Longitudes are in System II, drifts (DL2) in degrees per 30 days. In this system, the GRS was stationary at L2 = 67 until September, +1 deg per month since then.]

South Polar region to S.S. Temperate region [report for whole apparition]:

The CCD images appear to show a white South Polar Hood with a dark collar, as in previous years, but these features are exaggerated by the digital image sharpening (see 1997 report, in preparation).

A small bright pinkish spot was recorded on the north edge of the south polar collar, at 62 deg.S, looking very much like one recorded in 1997 at 60 deg.S. However, either the motion is very irregular, or there have been 3 such spots in succession. Either way, speeds have varied from 0 to -27 deg/mth.

From the south polar collar to the STZ, the region was mostly dusky and contained multiple narrow belt segments, and one sector of white S3TZ ~80 deg. long.

The principal spots were the 7 small anticyclonic white ovals at 41 deg.S, moving with SSTC as usual. Most could be tracked from 1997; one had disappeared and a new one had appeared.

S. Tropical region:

The GRS has not changed.

The p. end of the South Tropical Band has varied in position and definition. It was usually near L2 ~ 10 (at the site of a previous dark spot in STropC) or ~ 35; but over short periods of a few days, there was evidence of rapid prograding motion ranging from DL2 ~ -43 to -88. This indicates that the STBn jetstream was affecting the dark material of the Band locally, although the overall p. end was approximately fixed in the STropC.

The two turbulent cyclonic disturbances in the SEB continued. The first (the post-GRS SEB disturbance) occasionally showed new white spots near L2 = 108, moving with DL2 ~ -50 over a few days. The other (the mid-SEB outbreak) also showed new white spots, near L2 = 210, moving at DL2 ~ -75 over a few days. Following here, activity from the original source had declined, although one new white spot was seen on the track of the original source as late as Oct. 20.

N. Tropical region [report for whole apparition]:

Within the NEB, there are two rifted regions ~180 deg. apart. The more conspicuous moved with DL1 = +120 (DL2 = -110). It was ~40 deg. long but sometimes extended further p. The other rifted region was just a sector where a few small white spots or longer NEBZ segments were occasionally seen, and had similar NIC drift.

The NEBn was characterised by: (i) Sectors of very dark brown NEB(N), mainly seen alongside or following the passage of a NEB rifted region. (ii) Several dark brown spots or streaks ('barges') along NEBn: at least seven in May-June. Most dated from 1997; but they all diminished in size and/or intensity as 1998 progressed. They were not as well-defined as barges in some apparitions, being either small very dark spots, or streaks or bulges with ill-defined ends. (iii) A variable sector from L2 ~ 270-60. In this sector there were often minor features not listed in the table, whereas the listed dark spots were occasionally lost in longer NEB(N) streaks when a NEB rift had passed. This sector was also disturbed by the remarkable white spot Z.

White spot Z, one of the 'bays' in NEBn, was persistent although not always conspicuous, as it was moving through a region of variable dark streaks on NEBn. It had an exceptionally fast drift (DL2 = -11 to -9). It could be identified with a 1997 white spot with similar rapid drift, and/or a slower-moving white spot p. it; the former probably overrode or merged with the latter during solar conjunction, maintaining average DL2 = -10 throughout. Although the main white bay, like others, had a latitude of ~18 deg.N, it was accompanied by a tiny white spot due north at 20 deg.N, within the bluish N.Trop.Band. This latitude is more typical for anticyclonic spots in NTropZ and suggests that spot Z was more substantial than the other 'white bays'. As it moved along the NEBn edge, white spot Z seems to have greatly influenced the dark 'barges'. Following it were several mini-barges (esp. nos. 1 and 2), which had not existed in 1997 before white spot Z passed by, and which had positive DL2 in contrast to other NEBn barges. They were probably newly created in the wake of white spot Z where it destabilised the retrograding NEBn jetstream, and the spots were probably retrograding because they were interacting with this jetstream [cf. Voyager data, 'The Giant Planet Jupiter' chapter 8.4]. Conversely, white spot Z came up to and destroyed a tiny dark spot p. it, and then in October it impacted on the largest dark barge (a variable dark streak, no.7) which had persisted since 1997. This interaction was continuing in November.

North Temperate region:

NTBs jetstream spots:

This outbreak continued; five small dark jetstream spots were recorded, moving with DL1 = -63 (1). They all disappeared in Aug-Sep. Their demise was interesting: three of them became brown or even reddish, and sometimes diffuse, in their final weeks, and they were last recorded in this state as they passed the NTB rifts.

NTB rifts:

Two long oblique rifts were present from Aug.1 onwards. They moved at a constant speed DL1 = +87 (DL2 = -142), and thus repesented the North Temperate Current (NTC)-B -- a classic example of NTC-B appearing at the end of a NTC-C jetstream outbreak (though one such NTC-B rift was also seen in 1997).

This phenomenon was recorded from the 1920s to the 1940s, but not again until the 1990s. (In the intervening decades, NTBs jetstream outbreaks were much faster and had different phenomena; neither NTC-C nor NTC-B represents the full speed of the NTBs jetstream.) Modern images show that the NTC-B features are cyclonic rifts (occasionally containing a small white spot), similar to those of the NEB which also move at a speed intermediate between Systems I and II.

North Temperate Belt & Zone:

Apart from these rifts, the NTB was a solid dark belt. The NTZ consisted of long white sectors alternating with at least two long grey sectors, the latter being due to dusky grey NTZB streaks in the middle of the zone. There was a pominent dark bar of NTB(N) from Aug.26 onwards, All these features moved with the NTC-A.

N.N. Temperate region:

One remarkable spot was a tiny red oval on the NNTBs edge with DL2 = -41. It was only just resolved in colour images, but was bright in methane. It was just like a spot in 1997 with DL2 = -26, and the observations can be connected up through solar conjunction. So this was almost certainly a single long-lived spot of a type never before recorded, gradually accelerating towards the NNTBs jetstream speed. It was bright pink on 1998 Sep. 8 and 25, but last imaged on Sep.30 when it was barely discernible.

One more typical dark jetstream spot was imaged on the NNTBs, with DL2 ~ -73, but ony in 3 images over 9 days.

Also in the NNTB was a notable white oval, which appeared on Aug.27 on NNTBn, but soon interrupted the belt. It too had unusually rapid drift, varying between DL2 -14 and -22. Another NNTB spot was dark red-brown, with more typical NNTC drift, DL2 = +2. Being cyclonic by latitude, neither spot was bright in methane.

There were two more typical and long-lived white ovals in NNTBn or NNTZ, both anticyclonic by latitude, both bright in methane, with NNTC drifts of DL2 = -10 and -3. These latter 3 spots again demonstrate the gradient of speed with latitude that is sometimes observed within the NNTC [cf. 'The Giant Planet Jupiter', p.91].


A preliminary table of spots is being prepared. So far it consists of System II longitudes, drifts, and identifications from 1997 to 1998, for most spots. The format may not be suitable for e-mail. Please ask me if you would like a copy.


Oval FA
1998Aug07FAc295 degreesChristian Harder
1998Aug29FAc286 degreesChristian Harder
1998Aug31FAc284 degreesChristian Harder
1998Sep24FAc276 degreesChristian Harder
1998Oct25FAc258 degreesChristian Harder
1998Nov18FAc245 degreesChristian Harder
1998Nov21FAc245 degreesChristian Harder
1998Nov25FAp240 degreesWalter Haas
1998Nov25FAf243 degreesWalter Haas
1998Dec07FAp230 degreesWalter Haas
1998Dec07FAf239 degreesWalter Haas

1998Aug11Dc183 degreesChristian Harder
1998Aug25Dc172 degreesChristian Harder
1998Aug30Dc170 degreesChristian Harder
1998Sep04Dc164 degreesChristian Harder
1998Sep21Dc158 degreesChristian Harder
1998Oct19Dc144 degreesChristian Harder
1998Oct20Dc147 degreesChristian Harder
1998Nov07Dc135 degreesClaus Benninghoven
1998Nov07Dc134.6 degreesZac Pujic
1998Nov17Dc129.55 degreesDavid Moore
1998Nov18Dc128 degreesChristian Harder
1998Nov24Dc126.14 degreesDavid Moore
1998Dec06Dc124 degreesWalter Haas
1998Dec30Dc105 degreesJohn W. McAnally

STB Dark Feature #2
1998Nov17Df165.8 degreesDavid Moore
1998Nov18Dc161 degreesChristian Harder
1998Nov24Dp151.52 degreesDavid Moore
1998Nov24Df161.19 degreesDavid Moore
1998Dec01Dp148 degreesWalter Haas
1998Dec01Df160 degreesWalter Haas
1998Dec04Dp146 degreesWalter Haas
1998Dec04Df156 degreesWalter Haas
1998Dec30Dc123 degreesJohn W. McAnally

1998Aug30GRSc66 degreesChristian Harder
1998Sep20GRSc64 degreesChristian Harder
1998Oct26GRSc64 degreesChristian Harder
1998Oct29GRSc66 degreesChristian Harder
1998Nov05GRSc69.1 degreesZac Pujic
1998Nov07GRSC66 degreesZac Pujic
1998Nov12GRSc65 degreesChristian Harder
1998Nov17GRSc64 degreesChristian Harder
1998Nov19GRSc65 degreesChristian Harder
1998Nov26GRSc68 degreesJohn W. McAnally
1998Dec01GRSc66 degreesWalter Haas
1998Dec06GRSc68 degreesWalter Haas
1998Dec13GRSc66 degreesClaus Benninghoven
1998Dec27GRSc67 degreesJohn W. McAnally
1998Dec27GRSc65 degreesWalter Haas

Oval BE
1998Oct18BEc230 degreesChristian Harder

Note: The Jupiter Section of the A.L.P.O. has published an interim report of the 1998-1999 apparition of Jupiter, taking into account observations through October 1998. This report is available in Vol. 40, No. 4, of The Journal of the Association of Lunar and Planetary Observers, The Strolling Astronomer, pp. 163-166.

The A.L.P.O. Jupiter Section has also been tracking numerous other significant features on Jupiter in addition to that released through the IJW. This additional data is available to researchers upon request from the A.L.P.O. Jupiter Section.

John W. McAnally
The ALPO Jupiter Section
Acting Assistant Coordinator
Transit timings

STB DS #1 approaching conjunction with GRS.

As we continue to watch STB DS # 1, the spot continues to progress toward the GRS/RSH. Drift rates indicate that STB DS # 1 will be in conjunction with the preceding edge of the RSH on or about February 21, 1999. Conjunction with the center of the GRS/RSH should occur on or about March 5, 1999.

Even though seeing is becoming difficult and Jupiter is moving closer to the Sun, all observers are asked to continue observing. The behavior of STB DS # 1 as it meets the GRS/RSH is of keen interest and observations will be of great importance. These observations should receive the highest priority.

A sixth dark spot identified in the STB.

The South Temperate Belt and its environs continues to show a great deal of activity.

As previously reported, a 1999Jan02 CCD image of Jupiter by Antonio Cidadao of Portugal indicated that STB DS #2 was condensing into two, distinct segments. STB DS # 2 has been an elongated feature since its discovery. The two segments continue to span approximately the same distance in longitude, although becoming darker as the condensation has continued.

We have further designated these condensations as STB DS #2 Segment A and STB DS #2 Segment B. On 1999Jan02 Segment A was located at 127 degrees S2 and Segment B was located at 138 degrees S2, as scaled from Antonio's image. Observers are asked to observe these segments for continued morphology.

Another dark spot in the STB has now been identified with an accurate drift rate. This spot resides slightly south of the STB, perhaps in the northern section of the South Temperate Zone (STeZn). We have designated this spot as STB Dark Spot #6, as we have identified and confirmed six condensations during this apparition.

STB DS #6 is more condensed and slightly darker than STB DS #2, but not as dark or condensed as STB DS #1, which remains the darkest feature of the STB. STB DS #6 has been well observed since 1998Oct31, when we first identified it on a CCD image by Donald Parker. It was then located at 149 degrees, S2. Since then it has also been imaged by David Moore and Antonio Cidadao. It has also been seen visually by Claus Benninghoven. These observations establish a rate of drift very similar to STB DS #1 and #2, placing it in the same current.

Observers are asked to search their records for other observations which may correspond to STB DS #6, and forward them to the ALPO Jupiter Section.

We may be experiencing the dark material in the STB condensing into segments which later become more prominent spot-like features.


In response to the ALPO J-Net alert dated 1-25-99, two additional observations of STB DS #6 have been reported by astronomers. Both Damian Peach and David Moore have called attention to previous observations made.

A CCD image taken by Damian Peach recorded STB DS #6 at 181.2 degrees CM2 on 1998Nov10.

A CCD image taken by David Moore recorded STB DS #6 at 201.38 degrees CM2 on 1998Sept20. To date this image is the earliest sighting reported to the ALPO which clearly shows this condensation.

We gratefully acknowledge the contributions of these two, fine astronomers.

Observers are asked to continue observing and to continue examining previous observations and images for evidence of the condensation of this feature.

STB DS #1 and the GRS

A CCD image just released by Donald Parker shows STB DS #1 within 12 degrees of the following edge of the RSH. The image obtained on 1999Jan27 at 23:58 U.T. shows STB DS #1 at 94 degrees CM2.

This image supports the earlier prediction that STB DS #1 will be in conjunction with the following edge of the RSH on or about February 21st, just 23 days from now.

On the image, the STB and the southern edge of the RSH/GRS appear to be at about the same longitude. STB DS #1 should be in conjunction with the GRS on or about March 5th, just 36 days from now; however, the drift rate may change as this meeting occurs.

Again, we ask all observers to follow and report on the interaction of the spot with the GRS environ.

To: The DPS community and other interested scientists
From: Julianne Moses (
Subject: IJW "Laboratory and Theory" Discipline

The International Jupiter Watch (IJW) is an informal program created to encourage and coordinate studies of temporal variations in the Jovian system. Although observations constitute the backbone of the IJW, the program also provides a mechanism for the rapid dissemination of all types of theoretical, experimental, and observational information among scientists interested in the Jovian system.

The IJW consists of six working groups (disciplines) concerned with the (a) Io torus, (b) Jovian atmosphere, (c) satellites, (d) magnetosphere and radio emissions, (e) aurorae, and (f) laboratory and theory. Don Hunten, the chairman of the IJW steering committee, has asked me to manage the "laboratory and theory" discipline, which has been idle since 1995.

Experimental data and theoretical modeling are required for accurate interpretation of remote sensing data or for simulating complex processes. In spite of this need, the theoretical, observational, and laboratory communities within planetary science do not always communicate well with each other. It is my hope that the IJW laboratory/theory discipline will encourage interactions within the entire Jovian science community.

To achieve this goal, I have created a new IJW discipline Web site and will maintain a newsletter dedicated to current experimental and theoretical advances in our understanding of the Jovian system. The URL address is The Web site will contain newsletters, lists of recent publications, access to laboratory data in advance of publication, information on meetings of possible interest to discipline members, and links to other useful Web sites.

Anyone interested in subscribing to the IJW/Laboratory and Theory newsletter, which will be sent out roughly one a month (or as needed), should notify me at I also welcome submissions regarding unpublished laboratory data, references to recently published experimental or theoretical papers, links to other relevant URLs, and comments and suggestions on what to include in the site.

Images from Don Parker.

JUPITER IMAGES 23 Dec., 1998

D.C. Parker, Coral Gables, FL. Lynxx PC camera 16-in (41cm) f/6 Newtonian
Eyepiece Projection @ f/21.4
Integration Times:
Blue (Schott BG12 + IR Rejection) 1.88s
Green (VG9 + IR Rejection) 0.88s
Red (RG610 + IR Rejection) 0.73s
Images flat and dark corrected.
Seeing GOOD (6-8). Transparency 4.5m. Wind NE 2-4 kts. No dew.

JUPITER IMAGES 27-28 Jan., 1998

D.C. Parker, Coral Gables, FL. Lynxx PC camera 16-in (41cm) f/6 Newtonian
Eyepiece Projection @ f/21.4
Integration Times:
Blue (Schott BG12 + IR Rejection) 2.75s
Green (VG9 + IR Rejection) 1.20s
Red (RG610 + IR Rejection) 1.00s
Images flat and dark corrected.
Seeing GOOD (7-8). Transparency 0-4m with frequent clouds, haze.
Wind strong: E 6-13 kts. No dew.