[12] The GRS and spots moving around it,
The
Great Red Spot and spots moving around it (continued)
(analysis
mainly by Yuichi Iga)
Now
that Oval BA has passed the GRS, STB-2 lies alongside it, and a train of STBn
jetstream spots has been arriving at the f. end of both.
Yuichi Iga has analysed what happens to them.
The first two spots veered S to pass between the GRS and STB-2. The first
one changed to a white spot as it passed the S side of the GRS, and then
expanded into an orange cloud on the p. side of the GRS (Sep.21) – just like
the Baby Red Spot did in 2008 –before reassembling into a bright spot on STBn
prograding past oval BA. The second spot disappeared as it passed S of the GRS
(Sep.23). The third and fourth
spots changed into white spots when they reached the f. end of the GRS and STB-2
(Sep.26, Oct.1), then disappeared. The fifth spot also disappeared at the f. end of the GRS and
STB-2 (Oct.6). The sixth spot,
however, halted at this location and merged into the vertical dark line around
the f. side of the GRS (Oct.8). In
many of these cases, the last image of the jetstream spot resolved its
disruption as a tiny streak.
Although
all but the first spot disappeared alongside the GRS, traces of them did emerge
as a growing stack of oblique bright and dark streaks Sp. the GRS – especially
well shown in the v-hi-res images on Sep.28 (S. Ota) and Oct.3 (G. Walker) and
Oct.8 (I. Sharp, T.Barry in IR). At
least one of these has again rounded up to form another prograding bright spot
on STBn alongside oval BA (Oct.1-8). So,
the dark spots have all been disrupted, but traces of them survive and can
reassemble into vortices after the passage.
In
contrast, the conspicuous sixth spot, which merged with the narrow column just
f. the GRS, seems to have spread down it to generate a dark streak spreading f.
along SEBs on Oct.10-12 -- dissipating thereafter. Another STBn dark spot began
the same journey on Oct.18 (Fig.2).
Then on Oct.23-25, when the next spot arrived at the GRS, it was
distorted but did speed through the channel S of GRS, very fast.
Even more analysis could be done if anyone has time.
Bright
plume N of the GRS
(analysis
by T. Mishina & JHR)
The
bright white plume has erupted again N of the GRS, starting on Sep.22-23.
It was also seen bright in methane images on Sep.23 and Oct.3 (Tomio
Akutsu, Don Parker), though it was rather small and variable up to that time. Chris
Go first pointed out that the northern edge of the
GRS was very bright on Oct.6.
On
Oct.6, the plume was brighter in methane images (T.Akutsu & A.Yamazaki) and
also in visible light. On Oct.8-13 it was very bright in visible light, esp.
when near the limb, indicating its high altitude; a thin
dark
string was expanding west of (f.) this bright spot around the Red Spot Hollow as
far as the STB; and the blue triangle east of (p.) the plume was expanding to
the east. All these phenomena recapitulate previous appearances of this bright
plume.
It
was particularly bright on Oct.12 & 13, as Glenn Jolly and Chris Go both
remarked. The plume was also
methane-bright, and growing: The
E-W extent in methane images was 7500 km on Oct.12 (Yunoki, Yamazaki) and 13200
km on Oct.13 (Go), i.e. growth of 5700 km in 7 days.
It
sfaded somewhat after Oct.13, but was back in full force by Oct.23, when it was
well shown in the images by Tomio Akutsu and Don Parker, in both visible and
methane bands. As they pointed out, it was a very distinct methane-bright spot
on that date. By then it had become
quite extended in longitude.
On
Nov.6 (Sadegh Ghomizadeh & Chris Go), the white plume had disappeared (in
visible and methane). But the blue-grey
triangle Np. it was still very distinct.
We
don’t yet have recent measurements of the plume and its environs, but in July,
when the plume was present, the JUPOS chart showed several dark spots prograding
at DL2 ~ -80 to -90 deg/month within the blue streak or at its p. end.
This motion agrees nicely with what we found in 1990 Feb., when the p.
end of the blue streak extended at DL2
= -92 deg/mth for a few days.
_________________________________
John
H. Rogers, Ph.D.
Jupiter
Section Director,
British
Astronomical Association
jhr11@cam.ac.uk
http://www.britastro.org/jupiter/
_________________________________
