[22] Jupiter's SEB Revival in 2010/11: Analysis of the early stages of the southern branch
Report no.22 (final, 2011 April 6):
Jupiter's SEB Revival in 2010/11: Analysis of the early stages of the
southern branch.
John Rogers (British Astronomical
Association)
with data from Hans-Jörg Mettig, Gianluigi Adamoli, Michel Jacquesson &
Marco Vedovato (JUPOS project).
Summary
We present a preliminary analysis of the retrograding spots in the SEB(S) in the
early phase of the 2010 SEB Revival. Before the Revival there was a
continuous chain of small white spots separated by dark projections along the
SEB(S) with rather slow speed compared to the normal jet. ('Slow' and 'fast'
here refer to speeds in the westward, retrograding, direction.) At the
start of the Revival, the first dark spots in the southern branch appeared to
form from a few of these projections which suddenly darkened and
accelerated to full jet speed as they passed the source, without decrease in
latitude. Then, larger dark spots appeared from the turbulent region close
to the source, which also moved with nearly the full jet speed even though they
were up to 2 degrees south of the canonical jet peak, and they did not appear to
be vortices. Thus, the normal zonal gradient was violated as a band on the S
side of the jet peak suddenly accelerated. This band became the revived
SEB(S). Some of the dark spots drifted to the S edge of it and had slower
speeds more consistent with the usual zonal gradient. Subsequently, the
previous chain pattern re-established itself at the leading edge of the SEB(S),
still travelling more slowly than a dark spot that shifted from one projection
to the next. Similar behavior was probably occurring within the reviving
SEB(S), where chains of small bright spots like the pre-outbreak chain again
developed, probably with similar low speed, in spite of the dark material
retrograding more rapidly in the same latitude. Thus, there are several
surprising results from this analysis: the normal zonal gradient was changed,
there was no evidence for vortical motion, but there was sudden acceleration of
a broad band including pre-existing cloud-top features. This suggests that
the initial outbreak caused a sudden massive perturbation of the normal zonal
winds.
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John H. Rogers, Ph.D.
Jupiter Section Director.
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