May 27, 1997

Sun, 25 May 1997 16:01:36

From: Isao Miyazaki

I send you new images which were taken this morning. The seeing condition was not so good this morning. A STrZ white spot was located at P.end of the Red Spot.

40cm Newtonian, LynxxPC

Note: Miyazaki also sends these earlier images:

40cm Newtonian, LynxxPC

Sun May 25 01:32 MDT 1997

From Pedro Sada

We observed Jupiter's Red Spot transit on May 24th using the McMath-Pierce Solar Telescope (NSO/NOAO) while taking IR spectra of the planet (H2 quadrupole line at 518 cm-1). Seeing conditions were variable with gusty winds. We took some video with our guide camera through an OG-570 nm filter for contrast which we will digitize later.

During brief periods of steady seeing we observed the GRS and surrounding areas, looking for further effects of the White Tropical Oval (WTO) interaction. This is what we noticed centered at 10:45 UT on May 24th:

  1. The north half of the GRS is visibly brighter compared with previous visual observations. We estimated the area to be the same brightness as the neighboring South Tropical Zone (STrZ). Given the timescales involved with the GRS collar rotation (about a week), it appears that bright material from the WTO is circulating with the GRS collar wind field.
  2. The following side of the GRS was generally brighter than the rest of the Spot. We could hardly notice the division between the Spot and the STrZ at that point.
  3. We also noticed a small area within the GRS Hollow that was slightly brighter than the rest of the northern section of the Red Spot. It was most noticeable after the Spot had crossed the CM. It had circulated to a position angle of about 80 degress (+-10) north from the preceeding end.

This last point is interesting. This small area of brightness enhancement may be the same feature observed by us on May 21st and 22nd and also noticeable in the Miyasaki image of May 20th that was enhanced by Hernandez (see previous newsletters). If so then it is circulating around the northern edge of the GRS at a slower rate than the collar winds! Perhaps the WTO was so large that only part of it merged with the GRS. Another portion deviated equatorward around the Spot. If so, then it might "jump" the GRS and continue its westward motion in the next few days. Maybe it will be affected by the "wake" of the GRS. The Voyager GRS time sequence films shows both types of interactions between westward moving small eddies and the GRS. Some were absorbed while others deviated equatorward. Is there any record in the literature of this type of dual interaction between the GRS and a large eddy? Further confirming observations are needed.

Pedro Sada
Don Jennings

Sun, 25 May 1997 18:12:09 +0100 (BST)

From: John Rogers

Subject: The GRS-WO collision so far.

Many thanks to Isao Miyazaki and Don Parker who have e-mailed frequent images of Jupiter showing the progress of the interaction between the GRS and the white oval. The white oval remained poised on the preceding end of the Red Spot Hollow on May 12 (Miy.) and 15 (Par.). On May 20 (Miy., lo-res) and May 21 [Pedro Sada, report via IJW] it seemed to be moving into the Hollow. On May 22 (Par.) it seemed to be a bright white streak within the GRS itself, centred almost due north of the centre - consistent with the rapid circulation within the GRS. However Pedro Sada (USA, via IJW) and Yuichi Iga (Japan), also on May 22, reported it visually still in the north-preceding quadrant. On May 24 (Miy.), the most obvious sign is a bright notch again just preceding the centre of the Red Spot Hollow; but there are also new small light spots at both ends of the GRS, so the white oval may have broken up. Perhaps it has produced clouds eddying in various directions, or perhaps it has disrupted the smooth flow around the GRS; hopefully further (and higher-resolution?) observations will tell.

By the way, the previous history of this long-lived white oval in the STropZ (up to 1992) was summarised in 'The Giant Planet Jupiter' p.197 and Fig.10.41, and in our 1991/92 report [JBAA 104, 167; 1994]. When the SEB whitened before the SEB Revivals in 1990 and again in 1993, the white oval turned into a little red spot (see our bulletins for the IJW in 1993). After the 1993 SEB Revival, the spot reverted to a white oval, which was conspicuous and stationary (System II) near the longitude of impact site G in 1994, but it then recommenced the slow increase in longitude which has brought it to the GRS now.

-- John Rogers (BAA).