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Images of the Sun taken by the
Transition Region and Coronal Explorer

The TRACE images may be used without restrictions in publications of any kind. We appreciate an acknowledgement indicating that the Transition Region and Coronal Explorer, TRACE, is a mission of the Stanford-Lockheed Institute for Space Research, and part of the NASA Small Explorer program. More information on TRACE and other TRACE images can be found here.

A quiescent active region
This is a snapshot of Active Region 9114 observed with TRACE on 9 August 2000. The image was taken in the 171Å passband, and shows material around 1 million degrees. The associated 1.2MB

Quicktime movie (JPEG(Photo) compressed)

shows the rapid evolution of this region even though there were no obvious flares. The movie, showing the evolution from 13:17UT to 19:21UT, shows every 5th TRACE frame at only half the resolution, i.e. shown with ~750km for each pixel. The green circle (click here for an image without circles) is centered on a sunspot, that shows a bright ring at the umbral-penumbral interface in this image. This spot has been rotating gently for the several days that TRACE observed it, and the movie shows that that continues in these observations. This somehow triggers a magnetic reconfiguration leading to many rapidly evolving loops between the two circles. The red circle shows the reticulated, mossy emission pattern from the footpoints of hot loops. Note the rapid evolution of the brightness of that pattern in the red circles: first the emission fades, then a front moves over it from north to south, and then the cooling loops over it drain their material onto the surface, leading to a series of short-lived bright loop footpoints.
Bastille-day fireworks (2) Two-ribbon flare model
A major solar flare produced an arcade resembling a slinky. That flare has featured here before, but this time we are showing a set of composite images that shows the thermal evolution of the material. The X5.7 flare occurred at 10:03UT on 14 July 2000, in Active Region 9077, and was observed by TRACE in three colors: the red image shows the ultraviolet continuum, generally characteristic of cool, dense gas; the blue image shows the 171Å pass band, characteristic of material around 1 million degrees; the green channel shows material hotter than about 1.5 million degrees up to approximately 10 million degrees.

The top image is a collage of six images. Frame 1, right after the onset of the flare, shows very bright, rapidly evolving flare kernels and the beginning formation of ridges, or ribbons, that give this ``two-ribbon flare'' its name. Frame 2 shows an image around 10:25UT, 22 minutes later, when the ribbons have developed along much of their length, and loops connecting them are showing up on the right-hand side of the arcade. Frame 3 shows a bright ridge between the ribbons; this is presumably very hot material, but it remains unclear whether that lies below or above the now cooling loops connecting the ribbons. Frame 4 shows green loops forming on the left-hand side, that cool to blue in frame 5. In Frame 6 most of the arcade loops have cooled to around 1 million degrees.

Because TRACE observes gas of very different pass bands, it allows us in principle to perform a very detailed study of the thermal evolution of this flare, which was very large, and caused the largest particle storm of the cycle thus far. To get a feel for the intricacy of the development, look at the 1.3MB

Quicktime movie

(by Neal Hurlburt) to see the evolution of the magnetic arcade. Note that the exposures have been rescaled to the same peak intensity to show the evolution of the central bright region. This causes the surroundings of the flare site to apparently dim markedly as the flare reaches peak brightness. The field of view of the movie is 230,000 by 170,000 km.

The lower image shows a model of what may be happening (from Leon Golub): A filament rose through the overarching field, tearing it open in the process. The field then reconnects below the filament, releasing highly energetic particles that then travel down the field to cause the two bright ribbons as the particles hit the lower, denser material. Material evaporates into the loops, causing the bright, hot loops. As the loops subsequently cool, the green, hot loops, turn into cooler blue loops, and eventually will fade altogether.

Coronal rain
``Rain'' in the solar corona. Whenever the heating of the corona is temporarily stopped, the hot material cools down by radiation into space and conduction to the cool footpoints. As it cools, it slides down the magnetic field towards the solar surface. In this TRACE image (taken in the Lyman alpha passband on 29 May 1999) we see material falling down at a temperature of approximately 10,000 degrees, that is a factor of 100 cooler than the hot corona. The matter falls in clumps, showing up along only an occasional loop. In a four-hour interval, shown in this image, much of the field shows coronal rain. This image shows the maximum brightness at any one pixel during that four-hour interval; as a result, it looks like a stroboscope photograph, with particularly bright falling clumps showing up on successive locations as it falls, creating a flashing track.
Tornadoes and fountains EIT HeII 305 Pic du Midi hydrogen alpha
Hard to see on any single image, this prominence shows a marvellous combination of what appear to be twisters on the Sun evolving into a fountain of hot material towards the end of the 5.6MB

Quicktime (Cinepak-compressed) movie

that shows eight hours of the evolution of the prominence. The movie (observed on 2 August 2000 in the 171Å pass band of TRACE) shows cool, dark material embedded in the hot corona (as on the top image on the right). The cool material has a temperature probably close to 10,000 degrees and therefore shows up as a glowing structure in the SOHO/EIT HeII/304 and Pic du Midi Hydrogen alpha images - in the two bottom figures on the right (not on the same scale!) - which show singly ionized helium and neutral hydrogen, respectively. In contrast, the glowing, hot material in the TRACE images is at approximately 1 million degrees.

In the first half of the movie, the cool prominence material sloshes and twists in the magnetic field of the filament. In the second half of this movie, the cool gas southward of the two main ``tornadoes'' disappears, and the top part of the prominence becomes active and hot, and therefore bright in the TRACE pass band. An unusual fountain-like structure then forms at the top of the tornadoes. Hot material is thrown away from there, and then follows the arcs of the magnetic field as it slides down towards the solar surface.

Coronal rain (1) Coronal rain (2)
Two versions of the same image show what can be hiding in the dark. The images are taken with TRACE in the 1216Å pass band, containing Hydrogen Lyman alpha as the strongest contributor, of Active Region 9077 at the Western solar limb (rotated by 90 degrees, so North is to the left), taken at 8:57UT on 20 July 2000. The top image shows the solar image properly scaled for the signal on the disk, but the bottom false-color image shows how much weak emission is hiding in the dark. That signal would normally not be measurable if we exposed with a standard exposure that is good enough on the solar disk. But on extra long exposures (10 times longer than standard), the relatively dim material shows up clearly. Almost everything above the limb is material that is no longer heated, cools very rapidly, and falls down to the surface. Only a few structures in this snapshot correspond to material being thrown upward. Even that will turn into ``coronal rain'' shortly afterward.
Rapidly-evolving loops
This image is a 171 A image taken by TRACE on 25 July 2000, showing million-degree plasma. The image shows AR 9097 at 08:09 UT. There is a set of loops that formed around 08 UT, possibly brought on by a large flare that occured a few hours earlier. Note the very bright kernel in the southern loops; such a brightening is frequently observed in rapidly evolving loops, but its nature remains a mystery. Courtesy Dawn Myers.
Activated filament
TRACE 171Å image, showing emission from gas at 1 million degrees, of Active Region 9077 on 19 July 2000, at 23:30UT. The image (rotated over 90 degrees, so North is to the left) shows a filament in the process of lifting off from the surface of the Sun. The dark matter is relatively cool, around 20,000 degrees, while hot kernels and threads around it are at a million degrees or more. From footpoint to peak, this rapidly evolving structure measures 75,000 miles. Also the Astronomy Picture of the Day for 9 August 2000. There is also a set of three black and white images, showing the same scene in 171Å, 1600Å, and white light.
Fire away!
This image of Active Region 9077, which produced massive flares over the past few days, shows a relatively small ejection, along the arrow. The ejection appears to originate in a small, new magnetic region that emerges next to the large active region (just below the beginning of the arrow). In a period of some six hours, the region catapults matter up into the corona a dozen times. The ``bullets'' move with speeds of up to 600 km/s, or 25,000 miles per hour! Look at the 3.4MB

QuickTime (photo-JPEG compressed) movie

to see the ``heavy artillery'' in action. The movie shows the region in the 171Å passband (material at 1 million degrees), from 11:50UT to 15:30UT on 19 July 2000.
Sometimes coronal loops appear to move rapidly from one place to another. But what are we seeing here? Inside Active Region 9077 (seen in 195Å; 1.5 million degrees), there is a loop that appears to move from one side of a gap in the emission to another. Look at the 0.42MB

Quicktime (uncompressed) movie

to see the evolution of the loop within the magnetic arcade. Or is it a sequence of loops that lights up one after the other. Background radiation hitting the detector in the middle of the process is not conducive to a unique interpretation. The movie contains only 24 frames, from 09:43UT to 10:31UT on 15 July 2000.
Bastille-day fireworks
A major solar flare produces an arcade resembling a slinky. The X5.7 flare occurred at 10:03UT on 14 July 2000, in Active Region 9077, observed by TRACE in its 195Å pass band. A filament in the center of the region destabilizes and is seen lifting off. Following this mass ejection, an arcade of magnetic fields lights up, cooling down from many millions of degrees. Look at the 6.8MB

Quicktime (Photo(JPEG)-compressed) movie

to see the evolution of the magnetic arcade. Note that the exposures have been rescaled to the same peak intensity to show the evolution of the central bright region. This causes the surroundings of the flare site to apparently dim markedly as the flare reaches peak brightness. The field of view is 230,000 by 170,000 km. This image also featured on the Astronomy Picture of the Day for 20 July 2000.

Other TRACE images in this collection: Set 1, 2, 3, 4, 5, 6. 7.

See also a collection of images related to the Sun, other cool stars, and solar-terrestrial effects


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