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.
Grazing coronal eclipse in 171Å 2005/10/03
As it was the first to see the annular eclipse on 2005/10/03, so it was the last: the image shows the Moon covering the corona over the eastern limb of the Sun at 13:38:47 UT (rotated over +90 degrees, with north to the right). TRACE was moving southward in its orbit, so that parallax effects caused the Moon to move rapidly upward (or to the right in the rotated images) as seen projected against the solar corona. This short movie (0.3MB) shows how fast the Moon moved: the edge near the Sun is fairly sharp in these 32 second exposures in the 171Å channel, but the other edges are clearly blurred by the apparent motion of the Moon during the exposures.
Eclipse on 2005/10/03
TRACE observed the eclipse on 1005/10/03 even before it started on Earth: being in orbit above the Earth, and over the western limb at the time, the first image of the Moon covering the Sun was taken at 08:03 UT, while Earth observers had to wait anoter half hour befor the beginning of this annular eclipse. The white-light image shows the limb of the Moon, with mountain ranges clearly visible, against the north-western edge of the Sun. The circular edge at the bottom of the image is vignetting caused by the outline of the filter wheel that is projected onto the camera (the entire Sun is as large as the Moon viewed from Earth).

For more information on eclipses, visit Fred Espenak's eclipse pages.

Filament eruption in 171Å
The Transition Region and Coronal Explorer, TRACE, provides the highest-resolution images of the corona that are currently available (at 0.5 arcsecond pixels, or 1 arcsecond resolution). The instrument observed this filament eruption on September 30, 1998. The image, taken at 14:21:24 UT in the 171Å channel, shows a filament very early in its eruption, showing up dark against the backdrop of a arcade of loops; the big, dark filament is rising into interplanetary space with an increasing velocity that already exceeds 100 km/sec. These brightly glowing loops are the result of an earlier flare, cooling down from temperatures of several million degrees. As the loops cool, material drains from them, streaming back towards the solar surface under the influence of gravity. This is seen in this image as thin, dark strands of gas at approximately 10,000 degrees that absorbs the extreme ultraviolet emission from other, hotter gases behind them. This one image thus shows a range of temperatures that exceeds a factor of 100, with dark material both falling down and being thrust away from the Sun.

A high resolution (1600x1600 pixel) version of this image can be accessed here.

Filament eruption in 171Å 2005/06/16
Filament eruption in 171Å 2005/07/27

These two 2-h movies (movie (4.0MB) for 2005/06/16 19:00-21:00 UT, movie (3.5MB) for 2005/07/27 03:45-05:00 UT) observed in the TRACE 171Å channel, show two erupting filaments. The first show the far segment of an essentially circular filament destabilizing, and moving straight up into the corona. The second one shows an erupting filament that deforms the coronal field to the right of it, exciting rapidly-damped oscillations as the field adjusts to the rapid changes. The movies and images show only half of the TRACE full field of view (i.e., 512 pixels of approximately 720 km each).

X-flare in AR10808 in 171Å 2005/09/08
This 10-hour movie (30MB), taken in the 171Å channel, shows the evolution of a series of flares between 20 UT on September 8, 2005, through 06 UT the next morning. The largest flare is an X5.4 starting at 20:52UT, followed by an M1.0 at 02:08 UT, an M1.1 at 02:33 UT, an X1.1 at 02:43 UT, an M1.8 at 04:46 UT, and an M6.2 at 05:32 UT. Notice how the high loops to the right (north in the rotated movie) change in shape and even oscillate somewhat immediately following the X5.4 flare. The next three M-class flares hardly register in the TRACE image sequence. But the X1.1 is clearly visible. The final M1.8 flare and its aftermath show an interesting series of small ejecta, starting from the central flare region, being shot up into the coronal field, and either fading away or falling back down; we count at least 8 such events before the movie ends.

Click here for a listing (with links) to all the X and M class flares from AR10808.

X17 in AR10808 in 171Å (1)
X17 in AR10808 in 171Å (1)
Almost as soon as Active Region 10808 rotated onto the solar disk, it spawned a major X17 flare. TRACE was pointed at the other edge of the Sun at the time, but was repointed 6 hours after the flare started. The image on the left shows the cooling post-flare arcade (rotated by -90 degrees so that north is to the right) 6h after the flare (at 00:11 UT on September 8); the loop tops still glow so brightly that the diffraction pattern repeats them on diagonals away from the brightest spots. Some 18h after the flare, the arcade is still glowing, as seen in the image on the right (at 11:42 UT on September 8). In such big flares, magnetic loops generally light up successively higher in the corona, as can be seen here too: the second image shows loops that are significantly higher than those seen in the first. Note also that the image on the right also contains a much smaller version of the cooling arcade in a small, very bright loop low over the polarity inversion line of the region.

Click here for a listing (with links) to all the X and M class flares from AR10808.

X/M flares in AR10808 in 171Å

A record: most major flares in sunspot cycle 23:



Active Region 10808 has been a big surprise: this region, in the middle of solar minimum just as we thought solar activity was going to be low for a while, has presented us in a 11-day period with 10 X-class flares and 24 M-class flares. The image shows a composite of the first 9 flares observed by TRACE (M2, M2, X5, M1, M1, X1, M2, M6, X6) on 2005/09/08 and 2005/09/09 when the region was still near the eastern limb of the Sun (click here for a full-resolution version of 2304x2304 pixels). Each of the images was taken near the peak brightness in hard X rays as seen by the GOES satellite, which means rather early for the most spectacular TRACE images of the loops that form past the impulsive phase. But this composite shows where the flares started: notice how similar the magnetic configuration is, despite the repeated, disruptive flaring.

Active Region 10808 certainly deserves a place among the top flare producing active regions on record, with 13 major flares (i.e., M5 or greater), which is more than any other region in the currently ending Solar Cycle 23, and puts it in fourth place in recorded history. Powerful AR 5395 (March 1989) still holds the overall record with 20 major flares. AR 433 (July 1974) produced 17 major flares (note that AR 10808 produced a "double-peak" X1 flare on 12 September that went into the record as a single event; if we count these two separately, then AR 10808 would equal the recordholder AR 5395 in terms of the total number of 11 X-class flares). Region 3763 (June 1982) is in third place with 15 major flares. After fourth place AR 10808 we then find AR 5312 (January 1989) with 17 major events, AR 6659 (June 1991) with 12 major flares (five X-class flares saturated the XRS sensor at X12, while the sixth X-class flare was an X10), and AR 10486 (October 2003) with 12 major flares (including the largest flare on record - the X28 on November 4). [Statistics Courtesy of Bill Murtagh from NOAA's Solar Environment Center]

A sampling of these and images for all of the X and M class flares that TRACE observed from this region in the 171Å or 195Å channels can be accessed by clicking on the event numbers in the summary table below (which lists flare data from the NOAA event listings). Click on the 'SSE' (SolarSoft Event) flag following it to access a data summary, and 'Tmovie' to access summary TRACE movies (N.B. Not all events for which TRACE data exist were processed into movies by the automatic software).

8010 (SSE) + 1717 1740 1803 G12 5 XRA 1-8A X17.0 20050907
8160 (SSE)(Tmovie) + 1649 1703 1711 G12 5 XRA 1-8A M2.1 20050908
8180 (SSE) + 2023 2029 2041 G12 5 XRA 1-8A M2.1 20050908
8190 (SSE)(Tmovie) + 2052 2106 2117 G12 5 XRA 1-8A X5.4 20050908
8260 (SSE) + 0208 0219 0229 G12 5 XRA 1-8A M1.0 20050909
8280(Tmovie) + 0233 0236 0239 G12 5 XRA 1-8A M1.1 20050909
8290 (SSE) + 0243 0300 0307 G12 5 XRA 1-8A X1.1 20050909
8300 0446 0503 0512 G10 5 XRA 1-8A M1.8 20050909
8310 (SSE)(Tmovie) + 0532 0548 0600 G12 5 XRA 1-8A M6.2 20050909
8390 (SSE) + 0942 0959 1008 G12 5 XRA 1-8A X3.6 20050909
8500 (SSE) + 1732 1751 1810 G12 5 XRA 1-8A M1.9 20050909
8530 (SSE)(Tmovie) + 1913 2004 2036 G12 5 XRA 1-8A X6.2 20050909
8730 (SSE)(Tmovie) + 0606 0614 0617 G12 5 XRA 1-8A M3.7 20050910
8780(SSE) 0859 0907 0931 G12 5 XRA 1-8A M1.9 20050910
8850 (SSE)(Tmovie) + 1634 1643 1651 G12 5 XRA 1-8A X1.1 20050910
8900 (SSE) + 1910 1936 1950 G12 5 XRA 1-8A M4.1 20050910
8920 (SSE) * + 2130 2211 2243 G12 5 XRA 1-8A X2.1 20050910
8960 (SSE)(Tmovie) + 0229 0235 0240 G12 5 XRA 1-8A M3.4 20050911
9030 (SSE)(Tmovie) + 1244 1312 1353 G12 5 XRA 1-8A M3.0 20050911
9110 (SSE) * + 2029 2040 2049 G12 5 XRA 1-8A M1.3 20050911
9300 (SSE)(Tmovie) 0449 0505 0527 G10 5 XRA 1-8A M1.5 20050912
9310 (SSE)(Tmovie) + 0656 0701 0705 G12 5 XRA 1-8A M1.3 20050912
9330 (SSE)(Tmovie) 0837 0903 0920 G12 5 XRA 1-8A M6.1 20050912
9460 (SSE)(Tmovie) + 2005 2009 2011 G12 5 XRA 1-8A M1.5 20050912
9650 (SSE)(Tmovie) + 1041 1121 1124 G12 5 XRA 1-8A M1.3 20050913
9710 (SSE)(Tmovie) + 1919 1927 2057 G12 5 XRA 1-8A X1.5 20050913
9740 (SSE)(Tmovie) + 2315 2322 2330 G12 5 XRA 1-8A X1.7 20050913
9870 (SSE)(Tmovie) + 1005 1038 1054 G12 5 XRA 1-8A M4.6 20050914
0080 (SSE)(Tmovie) + 0830 0838 0846 G12 5 XRA 1-8A X1.1 20050915
0220 (SSE)(Tmovie) + 1855 1910 1926 G12 5 XRA 1-8A M1.0 20050915
0310 (SSE)(Tmovie) + 0141 0149 0156 G12 5 XRA 1-8A M4.4 20050916
0510 (SSE)(Tmovie) + 1735 1748 1810 G12 5 XRA 1-8A M1.3 20050916
0520 (SSE)(Tmovie) + 1918 1936 1948 G12 5 XRA 1-8A M3.520050916
0570 (SSE)(Tmovie) + 0558 0605 0615 G12 5 XRA 1-8A M9.820050917

Of these 34 large flares, TRACE missed the impulsive phase of the first (X17) flare because it was pointed elsewhere (but was repointed 6h after the flare start to observe the cooling postflare arcade), missed two partly while observing in 1600Å or 171Å offset from the main flare site, for two the onboard memory was full with information on earlier flares, while for two (marked *) the data was lost in transmission between the satellite and the TRACE computer system. But 27 of these large flares were observed by TRACE in either the 171Å or 195Å channels; sample images taken near the hard X-ray flare peak can be viewed by clicking on the event numbers in the above table (note that the file names contain pass band, date, and time information).

X17 in AR10808 in 171Å


Active Region 10808 has been a big surprise: this region, in the middle of solar minimum, has thus far treated us to 5 X-class and 7 M-class flares (see part of the X-ray light curve observed by GOES here). TRACE has observed all these but one of the X flares and one of the M flares. One image is shown on the left; more will be shown here later ...

Normally, solar energetic particle (SEP) events associated with disturbances in the eastern hemisphere are characterized by slow onset and lack of high-energy particles. The SEP event associated with the first major flare (X17) is shown in this image; it is among very few such events over several decades in that although the source region was on the east limb, the particle flux started to rise only a few hours from the flare onset, while the flux of protons with energies in excess of 100 MeV went up by more than a factor of one hundred. We do not understand how these energetic particles can reach the Earth from that side of the Sun, because there should be no magnetic connectivity.

ARs 9373/4 March 2001
AR9077 July 2000

When do electrical currents (and flares) occur in the Sun's atmosphere?

NASA press release 2005/08/16

Strong electrical currents in the Sun's corona form when new field, itself likely carrying currents, emerges into existing active regions out of alignment with existing field (see this study published in the Astrophysical Journal (ApJ 628, 501; July 2005).

The visualizations on the left (courtesy Goddard Space Flight Center, based on SOHO/MDI and TRACE observations), show the characteristic differences between regions with and without strong electrical currents. The movies first show the evolution of the magnetic field (observed with SOHO/MDI), then a computed current-free (potential) magnetic field, and finally the subsequent evolution as seen by TRACE in its 171Å pass band.

In the top movie, the computed field shows little resemblance to the coronal configuration observed with TRACE (gold color table); the strong currents responsible for this deviation between field and model caused very strong flaring activity in this region. In the bottom movie, the model field matches the corona quite well, and although there is considerable coronal variability, no major flaring occurred. The magnetogram movies differ in that the potential case shows some emerging flux, but relatively little, and mostly aligned with the pre-exising field. The non-potential case shows strong intrusions of misaligned, rapidly evolving field with very strong gradients. The latter characteristic is shared by almost all of the non-potential, flaring regions analyzed in the ApJ study.

X-flare in AR10792in 171Å 2005/07/30 05UT
TRACE observed the onset and evolution of an X1.3 flare in AR10792 in the morning of 2005/07/30. This 6-hour movie (21MB), taken in the 171Å channel, shows the evolution between 03UT and 09UT. The first two hours show the evolution of the northern filament (on the right in these images that were rotated by 90 degrees clockwise). Then, around 05UT, the lower (left-hand) filament erupts, throwing cool, chromospheric material upward, which shows the twisting evolution of the magnetic field before it slides down towards the limbward side of the configuration. Then the northern (righthand) filament erupts at the start of the hard X-ray flare around 06:20UT.

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, 21, 22, 23, 24, 25, 26.

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


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