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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.
(1) Evolution of AR10455 in 171Å on 5-16 Sep. 2003 (2) Evolution of AR10455 in 171Å on 5-16 Sep. 2003

Flux emergence and reconnection

TRACE observed the evolution of Active Region 10455 during its disk passage in September 2003. This (QuickTime/JPEG; 19.4MB) movie in 171Å shows the evolution during an 11-day period (Sept. 5 through 16), showing exposures taken roughly half an hour apart (the TRACE data base contains the full set at a cadence of under one minute). The movie shows the response of the corona to the emergence of new bipolar regions in two very different situations:

Around midday on September 10, a new bipolar region emerges just right of the center of the field of view, underneath the dark filament. Within hours of this emergence, the filament destabilizes and rearranges its endpoints (only one of which is seen in this cutout). By 19UT on 11 Sep., the filament disappears, and a weak (B7.9) flare follows: faint flare ribbons are briefly seen, followed by brightening loops early on 12 Sept. that show a peculiar kink before straightening out. But filaments are not easily defeated: fragments of it reform, and a faint darkening is seen where the original filament was as the region approaches the Sun's western limb.

Around 10UT on 12 September a new bipolar region emerges to the left of the center of the field of view. As it expands into the corona, new connections to the pre-existing field to the left/west are seen within some 9 hours after the emergence starts, shortly thereafter followed by connections to the south and then to the north-east.

TRACE/RHESSI: a gamma-ray flare
A superposition of a RHESSI image of gamma-ray and X-ray emissions (contours) with the TRACE satellite extreme ultraviolet image (green, negative color table) taken 90 minutes later of the July 23, 2002, solar flare. The superposition clearly shows the large separation between the high-energy emissions. Solar physicists expected to see X-rays and gamma rays emerging from the same spots at the base of the flare loops. Apparently, the Sun's magnetic processes are able to separate the electrons from the ions, sorting them either by mass or electric charge, as they blast them to almost the speed of light. The gamma rays seem to be coming from the feet of the large magnetic field loops, while the X-rays come from the feet of the small magnetic loops nested inside the larger ones. See the press release for the full story, at Berkeley, GSFC, or NASA.
X4.8 in 195Å on 23 July 2002
Revisiting a flare: the X4.8 flare that TRACE observed on 23 July 2002 was featured on these TRACE pages once before, but it turns out to be worth looking again. The (QuickTime/JPEG; 6.9MB) movie in 195Å shown here shows the flare at a very much reduced contrast (and flipped left to right), and with a much higher saturation threshold. Consequently, it shows the brightest flare ribbons and loops, rather than the surroudings of the flare that were visible in the other movie. What shows up at this scaling of the images that we did not see before is a fuzzy, relatively faint emission above the flare arcade in which there are rapid downward motions. We have seen this only once before, namely above the X1.5 flare on 21 April 2002. SOHO observations of that flare suggested that these dark regions are, in fact, voids that move downward, likely as a consequence of the reconnection that occurs in the wake of the eruption. But other than that, we still do not know what we are witnessing: this second event with this phenomenon may shed more light on that.
Movie by Dawn Myers.
Eruption in AR 10442 in 171Å
On 25 August 2003, TRACE observed a filament eruption in Active Region 10442. The (QuickTime; 5.7MB) movie in 171Å shows the initial, slow rise of the filament for about half an hour from the start of the movie at 02 UT. The eruption then becomes explosive between 02:28 and 02:32 UT. Within that interval, NOAA logged a GOES C3.6 flare in the region. Notice that the high filament material can be traced into the upper-left corner until at least 02:46 UT, where it casts a faint shadow onto the bright loops behind it. Courtesy: Dawn Myers.
Magnetogram of AR 10432; 18 Aug. 2003
TRACE 171Å image of AR 10432; 18 Aug. 2003; 09:00:01UT TRACE 171Å image of AR 10432; 18 Aug. 2003; 09:00:51UT TRACE 171Å image of AR 10432; 18 Aug. 2003; 09:01:41UT TRACE 171Å image of AR 10432; 18 Aug. 2003; 09:02:31UT
On 18 August 2003, around 09 UT, TRACE observed a small flare in Active Region 10431, using its 171Å pass band. The initial phases of the flare, shown in the four panels above, show a strong brightening of parts of a ring, forming the footpoints low above the solar surface of loops that are too hot for TRACE to observe. The magnetic field (shown on the left, with approximate positions and scale only), reveals why this flare occured with this particular geometry: a white-polarity intrusion exists within an otherwise black polarity area. This creates an ``anemone''-shaped ring of loops that end on the bright ring seen by TRACE. The magnetic topology is likely to have a null point floating in the corona above the center of the white-polarity intrusion (much like the configuration shown here); the central brightening may reveal that null point, or may lie low in the corona at the base of the flaring loops that are too hot for TRACE to observe. This event was pointed out by Sam Freeland, who also made a JAVA-script movie that can be seen here
Spot group in Active Region 10030 in WL
As active regions emerge onto the surface of the Sun, much of their magnetic field organizes into sunspots and their smaller relatives, the pores. This process can be very complicated, particularly if flux emerges into an alread existing active region. This (QuickTime/JPEG; 4.6MB) movie in white light shows five days in the life of Active Region 10030, with approximately one frame every hour (the movie runs from 2002 July 12 19:00UT to July 17 18:44UT). Note that TRACE tracks the region as it moves across the solar disk, so that the center of the image is always near the center of the active region; this leaves the distortion of the region as it is seen at different locations on the solar sphere, however, resulting - for example - in the apparent motion of the trailing (left) sunspot. Note also that the leading polarity of the new region merges with the existing sunspots, whereas the trailing polarity forms its own sunspot even as the existing one almost entirely disappears within the five-day interval that is shown here.
AR at the limb in 284Å
TRACE not only sees hot material in the corona, but often also relatively cool material at temperatures that are over a hundred times lower than those of the hot corona. This cool gas absorbs the EUV emission from the hot gas. It often shows up in the form of coronal rain, with loops draining after the heating stops. We also often see so-called sprays or surges: cool gas is thrust upward from the chromosphere into the corona, where it either heats up or falls back down. This (QuickTime/JPEG; 3.2MB) movie in 284Å shows a series of such surges near the solar limb that were observed on 21 August 2001.
Spot group AR9715 in white light
Sunspots evolve gradually on a time scale of many hours. That makes it hard to observe from the ground, with nights and periods of bad weather interrupting observations. It is easier from TRACE, for which interruptions only occur because something else of interest happens on the Sun and the telescope is pointed elsewhere for a while. This (QuickTime/JPEG; 11.7MB) movie in white light shows the evolution of the spot group in Active Region 9715, as observed from 0 UT on November 28, 2001, through 5 UT on December 6, 2001. This 9-day period (shown with typically 10 min. between frames, except for data dropouts and radiation-`damaged' frames) shows emerging flux, coalescing into a large, leading sunspot, and trailing smaller ones. By the time the region reaches the western limb of the Sun, most of the small spots and pores have vanished, leaving only the large, now apparently monolithic, leading sunspot.
M7.3 flare in AR10375 in 1600Å
TRACE observed an M7.3 flare in AR10375 on 12 June 2003, starting around 01:04 UT. This (QuickTime/JPEG; 10.MB) movie in 1600Å shows the development of the flare in the ultraviolet, at an average cadence of 5 seconds between frames. As the movie starts, a twisted loop emerges from the region, twisting and draining as it rises. Then, only some six minutes later, a second, smaller such loop is seen to rise. Following these events, we see the bright 'flare ribbons' evolve smoothly, flickering only because the exposure times change from frame to frame, leaving a small ripple on the movie signal. Courtesy Dawn Myers.
X-flare and particles

The Sun-Earth connection?

Active Region 10375 flared again: at 23:19 UT on 10 June 2003, an X1.3 flare was observed by TRACE in its 195Å passband. During these observations, the TRACE camera was hit by a storm of dangerous, high-energy particles (only a dozen other 195Å images have been recorded in the past three years that are that badly affected out of a total of 121,000). Did these particles originate from the solar flare? If so, how did the particles get here?

The possible connection, shown in the large image (smaller version here), may have started three days before the flare. At that time, our models of the solar coronal field (shown in panel A) showed that the solar wind leaving the Sun in the direction of the Earth was originated in the magnetic field of AR10375 (the red line traces the field from the region into the heliosphere). That wind flowed towards the Earth with a speed of order 500 km/s, taking more than three days to reach the Earth, and pulling a thread of magnetic field from AR10375 directly to Earth. When the flare went off, the Sun had rotated quite a bit, with AR10375 approaching the edge of the Sun (panel B). Any flare particles that reached into the open field would have flowed along the field pulled by the solar wind (see the top view in panel C).

What did TRACE see? Did the particle storm reach Earth just as TRACE flew over the Earth's magnetic pole, so that it was exposed to the storm without the protection of the Earth's magnetic field some 30 minutes after the flare as particles moving at about 1/3rd the speed of light went through the spacecraft, detector and all? Or is it merely a coincidence in which TRACE saw unusually many particles from within the Earth's magnetosphere fortuitously just after a major solar flare? Energetic particle sensors around Earth didn't see what TRACE saw: GOES 12 did see something in its electron flux measurements, but not particularly strong, and GOES 10 saw nothing - but then, these satellites are within the Earth's magnetic region, over the equator. ACE also did not see an energetic-particle event - but it is a million miles from Earth. Finding out what really caused the TRACE `snow' continues ...

(The model used to connect the Sun to the Earth is described on our space-weather forecast pages).

Active Region 10375 in 195Å
Active Region 10375 flared repeatedly: this (QuickTime/JPEG; 4.8MB) movie in 195Å shows a 1h 45m movie of the activity shows two C3 flares and an M2 flare (starting around 02:48 UT). TRACE observed interesting phenomena in this region even outside the big flares, however. Notice, for example, the repeated jets coming out from this region's leading (western) edge, moving towards the west and south-west. Some of these jets (visible as streaks blurred within the ~20-30s exposures) land near the region, others move along the field outside the field of view (of 640x480 pixels of 375km each). Notice also the oscillatory motions in the western(left)-most active region loops, bringing the total to at least 27 cases ( list of events).

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.

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


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