(Week 20, 1999)
See the weekly operations report for details.
In the display above (click to enlarge), the colored lines show the times of SXT images that currently are on-line at ISAS. The purple lines are flare mode. The gaps will be considerably reduced when the NASA telemetry arrives and gets reformatted.
For a summary index listing of the weekly science reports, click here.
which shows some of the dynamics.
In particular it appears that the right cusp element (idealizing the
geometry as an X for which the left and right sides don't quite meet)
actually exhibits flows along its length, from south to north.
This suggests that the "re-formation" of NS interconnecting loops,
a term often used by Z. Svestka, might result from siphon flow or
"evaporation" along basically stable magnetic structures.
The "re-formation" would then be interpreted as a "re-illumination."
Earlier in the week, on May 9, a rather nice cusp formed in the same general region, following a major LDE flare event in the active complex to the north. We show this as a movie:
The initial frame shows some of the flare, plus a lot of the saturation
and other systematic effects in the SXT detector that we don't normally
make public.
Note the time jump.
On the day after the flare, the cusp appears, and it grows to the E in
the usual pattern.
This seems like a textbook case of post-flare loop formation following
a CME eruption, with the remark here that the CME must therefore have
involved the entire heliospheric current sheet, as one frequently
observes in the
LASCO data.
We think we're learning things from watching these NS interconnecting loops. But what? Surely we see the results of reconnection, which is an inherently interesting physical process, but under what conditions is the reconnection taking place, why, and what results from it? No doubt the answers to these questions will help considerably in understanding how the complex "raw" magnetic field of the photosphere is cooked by the corona into the relatively simple solar-wind field morphology.
Note added in proof: today (May 14) this NS interconnecting structure has been developing interestingly. Glad we've been watching it!
Well (note added 5/17), the story did continue interestingly. Below is a difference image comparing May 15 (black) with May 17 (white), on a slightly exaggerated color display. It shows that, sure enough, the W limb did light up as the interconnecting loops re-formed beautifully!
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May 14, 1999: Hugh Hudson
(hudson@isass0.solar.isas.ac.jp)