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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.
AR 10655 TRACE/MDI composite
This composite shows NOAA active region 10655 on 3 August 2004, as observed by TRACE and SOHO. The four images show, clockwise from the top-left, the TRACE 1600Å image, the white-light image, and the 171Å coronal image, and the SOHO/MDI magnetogram. Contours show line-of-sight field strengths of 300G and 600G (dotted and solid for the two opposite polarities). Note, in particular, the fan of loops in the 171&ARing; channel ending in the central region of the leading sunspot. The dark wedge in the north may well correspond to the edge of a coronal hole, as suggested in this EIT image in which contours show open-field boundaries (the white lines are field lines going into the ecliptic plane; the dashed line is the projection of the heliospheric current sheet onto the solar surface). Composite image courtesy Etienne Pariat and Yuanyong Deng (Obs. de Meudon).
X flares in AR10720
NOAA active region 10720 appeared on the solar disk January 11, 2005. It grew to be one of the largest sunspot regions of the current solar cycle within two days of its emergence. AR720 released 5 GOES X class flares along with mutiple smaller events during the period between January 15-20 before it passed behind the west limb of the Sun. Here are a few samples of the X flares as TRACE saw them in the C IV 1600Å band and in white light. Courtesy Zoe Frank (LMSAL).
X7 in AR10720
Active region NOAA 10720 is one of the most flare-productive regions of the last few years, with 10 M-class and 5 X-class flares in a week. The largest flare (to date) from the region was an X7.9 on 20-Jan-2005, starting at 06:36 UT. The 53 min. movie (11MB) showing the UV evolution of the flare. Movie courtesy of Dawn Myers (GSFC).

The proton storm associated with this flare impacted many spacecraft. Not only those orbiting Earth were affected: the NASA Deep Impact mission en route to comet Tempel 1, even went into a safehold until the electronics could be restarted after the storm passed.

X3.8 in AR10720
Solar cycle flux
Even though the solar cycle is reaching its end (as can be seen in the flux diagram above - see our solar and space weather forecast), X-class flares still occur. The TRACE image on the left shows a 1600Å ultraviolet image of an X3.8 flare in AR 10720, that started at 6:59 UT. The image, taken at 7:43 UT, shows the large sunspot cluster in the center of the region (see the SOHO/MDI magnetic map for the global picture), with the flare developing right over its central regions. TRACE image courtesy Zoe Frank (LMSAL).
GOES x-rays 2005/01/02
X1.7 in NOAA10715; 1600Å

Fireworks for the new year:

The Sun started the new year with fireworks of its own: in the first minute of 2005, this X1.7 flare started in NOAA active region 10715 (shown in the GOES X-ray light curve on the right - click on it to see the full 3-day summary diagram). TRACE observed it in its 1600Å ultraviolet bandpass: the image above is the last frame from this 25 min. QuickTime/JPEG movie (2.3MB) showing the UV evolution of the flare from 12/31/2004 23:59:57 until 01/01/2005 00:24:45 UT. The flare caused no increase in electron or proton fluxes as seen by the GOES satellite; this was no surprise, as AR 10715 was at the time located at (N05,E34), and was neither associated with open magnetic fields nor near any such field that might connect to the Earth (see this rendering from our space weather forecaster).
X2.5 in NOAA10696; 1600Å
X2.5 in NOAA10696; MDI Magnetogram of NOAA10696; 1600Å X2.5 in NOAA10696; MDI - 1600Å

TRACE observed this X2.5 flare in NOAA Active Region 10696 on 2004, November 10. This 55 min. QuickTime/JPEG movie (14.2MB) shows the event as seen in the 1600Å channel at a cadence that is as short as 1.9s during the main eruptive phase of the flare from about 02:04 UT onward. The image on the left shows a negative, logarithmically scaled cutout taken at 02:09:20 UT, zoomed in by a factor of two to reveal the detailed structure.

The three images above show the flare at 02:09:20 UT in a different color scale (lag. intensity 95-2000DN), a scaled SOHO/MDI magnetogram (taken at 01:39UT), and a blend of these two images (511x511 pixels of 370km each). The alignment is approximate, moving the images relative to each other until the correspondence appeared optimal. Note that the bright UV regions in over the northern (red) polarity appear to span a gap in the magnetogram; the arch-like structures that connect the extremities of the corresponding emission region appear to reflect the magnetic canopy over a relatively field free patch of the solar surface. Note also that the left-most part of the upper intensity structure (over the red polarity) does not seem to map to an abvious magnetic structure. We are studying how that can be.

For comparison, the RHESSI light curves for the flare are shown in the image below.
X2.5 in NOAA10696; RHESSI

Something moving really fast; 171Å

Did TRACE see something moving faster than 3500 km/s?

This TRACE 171Å image, taken on 2003 August 25 at 03:39 UT, shows a streak spanning over 520 pixels. Ordinarily, we would identify such long, straight streaks with particle hits on the detector. But this one is remarkable, in that it starts exactly at the front of a small destabilizing filament (visible in this QuickTime/JPEG movie (8.9MB)), causing us to believe it is the blurred track of something moving really fast in this 55 second exposure. The track's length corresponds to 191,000 kilometers if that object was moving in the plane of the sky, and more if it was moving towards or away from us. That gives it a velocity of over 3,500 km/s (or 7.8 million miles an hour). [A similar events is shown here].

So is it a solar event? Particle tracks can be that long, see, for example, these cases: 1, 2, 3. Cases 2 and 3 both show clear intensity modulations along the tracks, and since case 3 is taken with no solar signal on the detector, that modulation can clearly occur somehow within the detector. So the length and intensity profiles of the track are inconclusive. What is the chance of such a long track starting from near the end of a solar event, roughly in the right direction: well to within 10 of a million pixels, to within, say, 5 degrees of the solar event has a probability of 1 in 7 million. In a sample of 2000 similar (171Å, 55s) exposures, we found 2 tracks longer than 500 pixels, or 1 in 1000. The probability that this is a random particle event is therefore 1 in 7 billion. As TRACE has made about 7 million exposures thus far, that leaves us with 1 in 1000. So it is rather unlikely to be a particle traveling through the detector, yet it is hard to believe something on the Sun could produce this image.

Partial eclipse 2004/10/14
This image was taken on 14 October 2004 at 02:37:08 UT in the 1600Å passband of TRACE during a partial solar eclipse: the dark area on the left of the image is the moon that covers a magnetically quiet area of the Sun in which bright magnetic concentrations outline parts of the supergranular convection cells. The slight darkening in the central part of the image shows the wear of the CCD imaging system: the many millions of exposures of the Sun that TRACE has taken so far have reduced the camera sensitivity to about half its value at the time of launch six years ago. Courtesy of Dawn Myers, GSFC.
3-color image of AR10673
Field extrapolation for AR10673 AR10673 in 171Å on 2004/09/23 at 19:11:06 UT AR10673 in 195Å on 2004/09/23 at 19:09:23 UT AR10673 in 284Å on 2004/09/23 at 19:10:06 UT

Open and closed field lines

The false-color image on the left is a 3-color composite image of AR 10673 taken by TRACE on 2004 September 23 (195&ARing; in red at 19:09:23 UT, 171Å in green at 19:11:06 UT, and 284Å in blue at 19:10:06 UT; the three separate images are shown above). The image shows a dark wedge south of the active region, which the PFSS model field suggests is in fact a coronal hole (see the green - open - field lines in the PFSS model in the field rendering above). Next to this coronal hole, on the lower, righthand side of it, are loops with a pronounced kink at their tops. These look like they are field lines that approach a cusp at the top of the closed-field domain, directly adjacent to the open field.
Sample flare

Flare catalog

TRACE has observed many flares during the past 6 years, some of which were shown here before (see the 304 image thumbnails for the 211 entries to date - 2004 September 17 - in the image archive and the associated movie set, also listed at the bottom of this page). In case you want to see more movies, learn about their properties, or find out about data obtained with other instruments, please look at the flare catalog. The catalog, complete for X and M class flares through the end of 2003, contains 51 X-class flares, 360 M-class flares. The C-class flare list, ending in November of 2002, contains 291 entries. The catalog was started by Kathy Reeves, and is now maintained by Jonathan Cirtain. The image on the left was taken in the aftermath of a large flare on 2001/04/10 at 07:07:02 UT.

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.

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


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