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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.

Corona and chromosphere
These images (taken on 21 March 1999) compare the corona (as seen by TRACE in the 171Å passband; 1 million degrees) and the chromosphere (as seen at Big Bear Solar Observatory in the hydrogen alpha line; some 10,000 degrees). The cool filaments/prominences show up as bright off the disk in hydrogen alpha, but as dark, absorbing features in the extreme ultraviolet image at the top.
Spot fields
This composite of observations was taken on 10 February 2000, at about 01:35UT. The lower image is part of a TRACE 171Å image, showing plasma at 1 million degrees. The red box ``B'' shows a so-called anemony field geometry, in which a pore (shown in the magnetogram in the green box, and in white light in the yellow box) of one polarity is surrounded by field of opposite polarity. In the case of the sunspot in box ``A'', however, the sunspot carries so much electric current that the field lines circle around it before entering its penumbra, not being able to simple dive into it in what should have otherwise been at least a partial anemone.
Solar flare (171Å)
This solar X-class flare was observed by TRACE at 16:43UT on 22 November 1998, in the 171Å passband (characteristic of 1-million degree gas; in gold, on the left), 1600Å UV passband (characteristic of thousands to hundred thousand degrees; in red on the right), and in the white-light passband (mostly visible light; in pale yellow in the right). The flare heats up an arcade of loops at the edge of the disk that light up in the extreme ultraviolet. They quickly cool down, and the material rains out of them. That the cooler material is seen in the 1600Å image is not unusual, but that it is dense enough to be seen even in the white-light channel next to the very bright solar disk makes this a rare event. The event was pointed out by Harry Warren (SAO, Cambridge, MA), who wrote a paper on this event to be published in Letters to the editor of the Astrophysical Journal. Solar flare (1600Å) Solar flare (white light)

Filament destabilization
Filament destabilization observed with TRACE, in the 171Å passband (1 million degree emission) on 16 April 2000. A small active-region filament near the arrow in panel a begins to destabilize at 03:43 UT; at this time it is still cool (some 10,000 degrees) and dark as it absorbs any coronal emission coming from behind it. The filament rises (with an average velocity close to 70 km/sec, or 250,000 km/hour), and material in it heats up to coronal temperatures (panel b). Then, within about 8 minutes (panel c), the filament shows its connections to distant fields, much of the material heats up, and material moves along the nearly horizontal field towards the lower-right in the images (which have all been rotated over +90 degrees for clarity). It only takes a few minutes for much of the material to cool down again to some 10,000 degrees, so that it absorbs much of the emission from behind it (panel d). It then begins to drain from the high loops, falling down towards the surface, mostly at the original filament site, but some of it slides down towards the distant footpoint (panel e). After approximately 2 hours, all seems to have returned to the original state. Larger version of the individual images: a, b, c, d, e, f. Each panel shows 440x440 pixels, of 375 km each.
Solar flare
This solar flare was observed by TRACE at 03:30UT on 12 April 2000, in the 171Å passband, characteristic of 1-million degree gas. The image on the left was taken shortly after the flare started. It shows the primary flare site just right from the center. Very fast beams of energetic particles traveled along the field lines toward the left, which upon impact on the lower, cooler atmosphere light up along a curved track. That track is more easily seen on the right. This is the difference between the image at 03:33:22UT and at 03:31:51UT. Where it is white, the image brightened; where it is dark, it became dimmer. It shows that the flare site is connected to a dome of field lines, ending along the ridge on the left; this dome is presumably a separatrix, that is, a surface that separates field lines that connect to different magnetic concentrations on the solar surface. The difference image also shows that loops are distorted by the flare. The so-called moss, the footpoints of loops that are too hot to see in this image, have moved about rapidly in the short time interval, causing the black-and-white reticulated pattern at various locations in the image. Click here to view the difference image without annotation. Flare brightening

Mercury transit
A collage of images taken with the Transition Region and Coronal Explorer. The images are taken in the 171-Angstrom channel (Fe IX/X; characteristic of material at approximately 1 million degrees), the 1600-Angstrom passband (UV line and continuum emission; mostly showing material at around 5500 degrees on the disk, and material at about 100,000 degrees just above the solar limb), and a broad-band white-light channel (around5500 degrees). Note that whereas the planet Mercury just comes within the edge of the Sun in white light, it comes much further onto what appears as the disk in the extreme ultraviolet (EUV) image at the top: the offset between the white-light and EUV limbs is approximately 4,000 (plus or minus 200) km. This is caused by the envelope of chromospheric material immediately above the surface: white light goes right through is, but EUV light does not. The EUV doesn't shine through until much higher. This demonstrates clearly that the Sun is just a gaseous sphere without a well defined surface: at different wavelengths the Sun has a different size.
Solar eclipse
This TRACE image taken in visible light shows the start of the solar eclipse of 11 August 1999 (image taken at 09:09:13 UT). The moon is just beginning to cover the Sun, starting at the north pole (an effect of the TRACE orbit over the Earth's terminator). The image is sharp enough to see the mountains on the edge of the moon, and the small (1,000 km) convective cells on the solar surface, called granulation. Note also the darkening of the solar disk toward the edge.
Active-region corona
The image on the left is a 171Å image taken by TRACE on 4 April 2000, at 13:10UT, showing plasma at approximately 1 million degrees. The image shows Active Region 8939 near the central meridian; the field of view is 290,000 (800 TRACE pixels) to a side. The image on the right shows the ratio of the 191A to 171Å images, displayed logarithmically, ranging over a factor of three up and down from unity. That images shows the temperature of the emitting gas; the coolest material is shown in red, warmer in green, and the hottest in blue. The brightly emitting fans of coronal loops emanating from strong concentrations of magnetic field on the surface are coolest, getting somewhat warmer with height. The warmest plasma is found over the patches of ``moss'' in the 171Å image. This ``moss'' is formed by the lower parts of loops that have temperatures of 3 to 5 million degrees. The moss is the layer between that hot material and the much cooler chromosphere below. The diagonal ripples in the outer parts of the temperature image are an instrumental effect, also seen weakly in the 171Å on the left. Click on either image to view the pair side by side. Click here, and here to view the full-sized images separately. Coronal temperature structure

Corona at the limb
This image (with another color table on the right) of coronal loops over the eastern limb of the Sun was taken in the TRACE 171Å pass band, characteristic of plasma at 1 MK, on November 6, 1999, at 02:30 UT. The image was rotated over +90 degrees. This image was also the Astronomy Picture of the Day for 28 September 2000. Corona at the limb

A full-disk mosaic
The solar corona as observed by the Transition Region and Coronal Explorer (Handy et al., Solar Physics Vol. 187, p. 229; Schrijver et al., Solar Physics Vol. 187, 261) on 29 June 1999 around 02 UT. This mosaic is made up of 3 exposures at each of 23 pointings. The green, blue, and red color tables in this ``true color'' image represent the 171 A (1 MK), 195 A (1.5 MK), and 284 A (2 MK) channels, respectively. The image was prepared by J. Covington (Lockheed-Martin Missiles and Space, Palo Alto).

Other TRACE images in this collection: Set 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

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


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