Header image

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.
Venus transit 2004
Venus transit teardrop effect in WL

On 8 June 2004, TRACE observed the transit of Venus across the disk of the Sun. Follow this link to a website that describes the event and will show TRACE observations as soon as the data are available in our archives.

NASA image gallery feature.

Quiet Sun magnetogram
Anything that is not a strong, large bipolar active region is called 'quiet Sun.' With TRACE, however, nothing there is particularly quiet. The (QuickTime/JPEG; 13MB) movie in 171Å shows 3 1/2 hours of quiet Sun. The region (outlined in the magnetogram taken by SOHO/MDI to the left - click for a full-disk version) contains enhanced network in which bright and dark structures evolve from moment to moment. To the north and east (left) there are filament-like structures, showing flows and rearrangements, and 'feathers' of fibrils presumably landing on the mixed polarity network. It is surprising how little of these filaments shows up on the H alpha image taken at Big Bear Solar Observatory that day.
ARs 10581 and 10582
Neighboring Active Regions 10581 and 10582 did not flare spectacularly, but this sequence of small flares (C1.1, B6.4, C2.0, C3.8) is interesting, nevertheless. The (QuickTime/JPEG; 13MB) movie in 195Å shows the evolution from 21 UT on 30 March 2004 until 03 UT the next morning; the pixels are twice as large as normal (here 725 km to a side). The weakest of these flares is, in fact, the most intriguing event. Starting at 22:45 UT, the southern region undergoes a filament destabilization: rolling motions are followed by brightening of the filament structure, and then the brightening turns into flare ribbons that spread out. Simultaneously, the outer loops move, as if they were opened by an erupting structure. Then a set of cooling post-eruption loops brightens across the filament, suggestive of reconnection. During this process, another event (C3.8) occurs in the northern region. These events were suggested for this POD by Alana Sette, SAO.
1600Å pre-annealing
1600Å post-annealing 171Å pre-annealing 171Å post-annealing

TRACE gets better vision for its 6th birthday

In the course of time, the TRACE detector showed an increasing number of 'warm pixels' with increased background levels. To counteract that effect, the TRACE team warmed up the detector for three days, from 17 through 19 of March, 2004, from the usual operating temperature of some 60 degrees Centigrade below freezing to 40 degrees above. We found that the number of 'warm' pixels had decreased by about a factor of three.

Another effect of this so-called detector annealing is that the overall sensitivity of the detector has increased by about 30-50%. The sensitivity had decreased gradually over time, down to about 30% of the original sensitivity in the center of the detector, and to about 80% at the edges. If the magnitude of the improvement proves correct after more detailed analyses, then the three-day 'spa treatment' has reduced the detectors effective age by about a year and a half.

The numbers: The reduction in the number of 'warm' pixels is best seen in the corners of the two (yellow) 171Å images. The increase in sensitivity is most readily seen in the central areas of the (red) 1600Å images, but also in the 171Å images, although part of the change may be an intrinsic evolution of the solar corona. The first two (red) images are 1600Å exposures (both 1.22 s) of the solar north polar region. The last two (yellow) images are 171Å exposures (46.4 and 32.8 s, respectively, shown normalized to the same exposure duration). The average signals (above the detector threshold) over the central half of the images is some 50% higher in the post-annealing 1600Å image, and 30% higher for the 171Å images. The exposures were taken on 27 February and 23 March, 2004, respectively, approximately one solar rotation apart.

Pre-X flare in AR 10564 in 171Å
X flare in AR 10564 in 171Å

On 26 February 2004, TRACE observed an X1.1 flare in Active Region 10564. The images above show pre-flare and post-flare conditions, having been taken at 01:41 UT and 02:17 UT, respectively, with the flare peaking at 02:03 UT. The (QuickTime/JPEG; 5MB) movie in 171Å shows the evolution of the loop structures at the flare site. The exposure durations are 23 seconds in all frames, but the display scale is changed once the flare starts so that the flare loops do not saturate in the movie. Images and movie courtesy of Dick Shine and Zoe Frank.

X-point in AR10561 in 171Å?
The interaction of neighboring magnetically active regions causes the solar corona to reconfigure its connections all the time. Although it must be a common process, we do not often get a chance to see how it really happens. This movie in 171Å of Active Region 10561 and surroundings shows us a glimpse of this process, we think. The movie suggests the existence of an X-point in the magnetic field (near the center at the bottom of the field of view, which spans 10,000 km to a side). As time progresses, a new set of loops appears (outlined in green in the still image to the left), startin around 8 UT. This set of loops may well be field that originally closed within the magnetic region, closer to the solar surface than the location of the X point. That field then appears to migrate through the X point, now connecting to fields much further away.
Megaflare 2 in AR 10486 Megaflare 2 in AR 10486: WL+195Å overlay
: largest soft X-ray flare observed to date.
Only a few days after TRACE observed its first official "megaflare" on 28 October 2003, Active Region 10486 produced one that was even stronger (click here for the GOES X-ray light curve). This flare was at first classified as X17.4, but that later revised to an estimated X28; if that classification is correct, this is the largest soft X-ray flare ever recorded.

The (QuickTime/JPEG; 7MB) movie in 195Å shows the evolution of the flare, seen at the solar limb (images rotated by +90 degrees). Another (QuickTime/JPEG; 8.4MB) movie shows the evolution in the 1600Å channel (same orientation, but not aligned; movie by Zoe Frank, LMSAL). The two images to the left show the cooling arcade after the flare in 195Å (top) and an overlay of the white-light image (in yellow) and the flare as seen in 195Å. Here are a few snapshots taken at 19:53:40, 20:08:51, and 20:12:39.

Megaflare in AR 10486
: third largest recorded until then (but see the entry above!).
TRACE observed its first official "megaflare" on 28 October 2003. Active Region 10486 had been treating us to multiple large flares in the days before as a result of its magnetic complexity (AR10486 is the region southward of the MDI high-res field of view shown by the white square in the magnetogram), so we were expecting more fireworks! And then there was this X17 flare.

The (QuickTime/JPEG; 17.4MB) 3-hr movie in 195Å shows the evolution of the flare: It begins with some compact loops in the center of the field just after 10 UT. That is followed within 15 minutes by several flare ribbons that brighten, and rapid motions and brightenings around the filament towards the lower right. The beginning of the main event complex occurs just as TRACE cannot observe for about 25 minutes; when observing resumes, there is a fuzzy set of loops just left of center. Around 11 UT, many new flare ribbons right of center show up (so bright there are multiple diffraction patterns seen in the images). Again there is an interruption in the TRACE observations: 12 minutes later, a bright post-flare arcade is formed, that cools and drains with time. During that last phase, there is one more period when TRACE cannot observe, because the Earth moves in front of the Sun; the fainter images that beautifully show the cooling arcade when observing resumes, are observed through the Earth's atmosphere. As TRACE moves away from its eclipsed views, the loops brighten again as the Earth's atmosphere blocks less and less of the light.

Click here to access the NASA press release, here for the ESA press release, here for the frames from above TRACE movie, or use these for two other movies: movie in 195Å (13.7MB), movie in 1600Å (13.8MB).

X1.3 flare ribbons
On 27 May 2003, an X1.3 flare started around 22:56 UT, according to the NOAA event listings. This flare occured in an unusual magnetic configuration (see the high-resolution magnetogram somewhat earlier here): black polarity field wedged between two white-polarity ridges. The flare was associated with a field eruption around 23:00 UT, which TRACE observed in its 1600Å passband. EUV observations of the region did not start until about 00:40 UT on 28 May; one of the first of these images is shown to the right. It reveals a double arcade of loops, cooling and draining after the flare: the coronal magnetic field shows a double arcade structure, with a well-defined magnetic separatrix running in between, apparently not far from a potential-field state. Note that this separator is also visible in the earlier EIT 284Å image.
Quiet Sun in 171Å
The so-called quiet Sun has not received much attention in this collection of TRACE imagery ... yet. But here is an example that illustrates the complexity of these regions that cover most of the solar surface: this (QuickTime/JPEG; 1.0MB) movie in 171Å shows the evolution of a region of very quiet Sun that was observed on 4 May 1998, early in the TRACE mission. These deep exposures (with exposure times ranging from 46 to 131 seconds) summarize the evolution of the multitude of coronal loops that exist between the magnetic concentrations that cover the quiet regions of the Sun over a period of just over 5 hours. The long exposures often have radiation hits in them that degrade the images, despite the application of a correction algorithm (the worst frames were deleted altogether). The movie illustrates just how complex the quiet Sun really is, and how frequent the many interactions between them change shape (a detailed study showed that the coronal pattern over quiet Sun in fact decorrelates completely on a time scale of no more than 15 hours). For examples of another quiet-Sun region, with magnetic information overlaid, click here, and scroll to the bottom of the main frame.

Other TRACE images in this collection:
Set 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

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


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