[6] Report on the NTB outbreak (June 2012.)

Major outbreak on NTBs jet-stream

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):

“Manos 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....”

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 observers’ 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. 

 
_________________________________

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