The time span is 16:37 UT to 16:52 UT, on 3-Nov-00. These images are extracted from the SXT half-resolution full-Sun frames, so each pixel corresponds to a distance of about 3400 km (in the plane of the sky, at the distance of the Sun). To get a closer look, we have two options: (i) blow up the SXT images, or (ii) grab images from TRACE, which has a sharper eye. The results of both these are below. First, doubling the size of the SXT images yields this movie:
Right away we start to see some interesting details. First this jet is a "repeater", meaning that after the first eruption, there is a second brightening. This is fairly common.
Second, the jet is not perfectly straight. It's slightly curved to the west (right), and even appears to change shape as it progresses. The path and shape are determined by the magnetic field which confines the hot plasma -- an open question is whether the other end of this magnetic field is located on the Sun, some distance away, or far out in space (i.e., is the field closed or open?). In the present case, we believe the jet is open to space.
There is a hint of substructure in the base of jet, meaning that there is physics happening on length scales smaller than 6800 km. It is difficult to tell from these images, however, because there's also a hint of saturation in some of the pixels.
The sharper eye allows us to see that there is a lot of structure in the jet plasma, and in the region at the foot of the jet. The whole region at the base of the jet seems to be erupting, reminiscent of a filament eruption. The higher cadence (i.e., more images per minute) suggests that as the clumpy plasma moves outward along the magnetic field lines, its path is helical and twisting. At the end of the movie, we can see the foot-region brightening again, in preparation for the second "spurt" observed at the end of the SXT movie. We even get the impression that the jet "conduit" itself is glowing faintly, it presence evidenced by plasma bound to its magnetic field. Let's take a closer look.
The path of the jet does seem to have some helical structure, as suggested in the first frame of the movie. But more interestingly, the spatial resolution reveals the connectivity of the magnetic field at the foot of the jet. Please consult the image below, taken from the middle of the TRACE full-resolution movie:
In the foot of the jet, there are coronal loops stretching from one side of the foot region to the other. The dipolar nature of the magnetic field is made apparent, despite the fact that this event is defined by material flowing out into space. Go back and watch the movie again -- you may be able to see the evolution of loops connecting the opposite sides of this foot region. And yet the footpoints of these loops do not leave the boundary of the "conduit". It just so happens that MDI has magnetograms from this time span, but at the time of this writing the analysis is not yet complete. So we will have to wait for a definitive explanation of the connectivity of the magnetic field. In the meantime, we can pile up a load of guesses: clearly, a cartoon is called for here!
This is not so different from previous explanations of jets, like the cartoon of Heyvaerts, Priest, and Rust, or the works of Shimojo and Shibata. In this case, we are simply placing the emergence of flux entirely within the collection of previously-open field lines, and not allowing it to stray outside. Mix in some reconnection, add just a pinch of rank speculation, and voila! -- a cartoon explanation. Quod erat faciendum.
November 10, 2000David McKenzie <email@example.com>