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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.

Looking back at the remarkable solar activity in the Oct./Nov. 2003 period:

Over 140 major explosions (or flares) occurred on the Sun during the period from 2003 October 18 to 2003 November 5. There were 11 large X-class flares during this period, each 30 to 600 times brighter than the entire non-flaring X-ray Sun in the 1-8Å pass band. These flares were associated with 6 major radiation storms around the Earth, as well as with 4 major geomagnetic storms. Among them we find the brightest X-ray flare ever, the 4th-largest radiation storm ever, and the 6th-largest geomagnetic storm. This period of solar activity also saw some of the fastest coronal mass ejections of the cycle, with mass thrown into interplanetary space with speeds reaching almost 10 million kilometers an hour, some four times faster than the average value. The composite image on the left shows the Sun on 2003 October 29 at 21:42 UT, one hour after an X10 flare, as observed by SOHO's EIT (green image), and the corona around it as observed by SOHO's LASCO (red and blue). Solar protons from an Earth-directed coronal mass ejection cause the speckles in the CCD detectors of the SOHO LASCO camera.

The large geomagnetic storms triggered by the solar mass ejections in the 2003 October-November period caused multiple problems with spacecraft orbiting the Earth or in deep space. The Japanese ADEOS-2 environmental observation satellite failed at the time of an intense interplanetary shock passing the Earth. Research and monitoring satellites like ACE, AQUA, Chandra, CHIPS, Cluster, DMSP F14, FedSat, GALEX, GOES-9, -10, and 12, INTEGRAL Mars Explorer Rover, Microwave Anisotroy Probe, Polar, RHESSI, SIRTF, SMART 1, SOHO, Stardust, TRMM, UARS, Wind, and the X-ray Timing Explorer went into safe modes or experienced high bit error rates, but fortunately they all recovered. The NOAA 17 and the Mars Odyssey mission each lost an instrument. A Japanese data relay satellite was shut down for over a week. The Inmarsat communications satellite had multiple anomalies. The astronauts in the International Space Station were ordered into the aft portion of the station five times during this time interval. Power-grid operators on Earth modified their sytem operations to avoid damage and outages, and nuclear power stations reduced their power output or delayed power switching. GPS users experienced difficulties, including such users as a deep-ocean drilling ship. Satellite communication systems experienced difficulties and airplanes were diverted to avoid dangerous radiation and communication outages. The origin, evolution, and consequences of solar activity like this is the focus of the NASA Living With a Star Program, complemented by observatories on the ground and in space, including the Solar-Terrestrial Probes, Earth observing systems, and probes throughout the planetary system.

[Image from a NASA/GSFC top story.]

NOAA Active Region 10486

This large sunspot group in NOAA Active Region 10486 was the source of incredible activity in the period from October 19 through November 7. By October 28 (see insets), the region had grown to the largest sunspot group of its solar cycle, and the largest observed since 1991. The main image shows the sunspot group as observed by the Dutch Open Telescope on La Palma on 2003 November 2, as it approaced the edge of the solar disk (image rotated by 90 degrees counterclockwise).

The insets show the visible-light, full-disk image of the Sun (yellow) and a corresponding magnetic map for 2003 October 28 at 17:36 UT (observed by MDI on board the ESA/NASA SOHO satellite). The large sunspot group in the southern hemisphere is NOAA Active Region 10486. By October 28, the region had grown to the largest sunspot group of its solar cycle, and the largest observed since 1991. The magnetic map shows the complex magnetic structure of AR 10486. The two polarities of the field in this region (displayed as red and blue) are not separated as in the smaller active regions surrounding AR10486, but are mixed in a complex pattern that is generally indicative of a propensity to flare. The multitude of small streaks and dots (best seen near the limb) are caused by flare particles passing through the MDI detector.

[Image from the DOT home page; click here for a version with 2920x2920 pixels).]



The solar chromosphere

The chromosphere of the Sun as seen in light of the hydrogen alpha line. The observation was made by the Big Bear Solar Observatory on 2003 October 28 at 15:42 UT. The chromosphere is a layer immediately above the surface as we see it in visible light, with temperatures typically around 10,000 Kelvin. Active Region 10486 (near the central meridian in the southern hemisphere) shows bright regions, called plage, over most of the magnetic field, surrounding dark sunspots. The dark arches in its surroundings are filaments, in which cool chromospheric material is suspended some tens of thousands of kilometers above the solar surface by magnetic forces.

[Image from the BBSO web archive.]

Largest recorded X-ray flare

The largest X-ray flare on record occurred on 2003 November 04. This image of the solar corona was taken by the Extreme-ultraviolet Imaging Telescope (EIT) on the ESA/NASA SOHO satellite at 19:48 UT. It shows the bright flare in progress at the solar limb, 11 minutes before it reached its maximum X-ray brightness. The flare caused the overall X-ray brightness of the corona to increase 600-fold in a matter of minutes. This caused the camera to be substantially overexposed, leading to an image artefact in the shape of a bright streak centered on the flare.

The line graph in image 1 below shows the solar X-ray flux (10-70Å, in milliwatts per square meter) measured by the NASA/SORCE photometer during the two-week period of high activity compared to the much quieter time before. At the other end of the spectrum, the microwave radiation associated with the flare was observed by the TMI microwave imager on the Tropical Rainfall Measuring Mission (TRMM) satellite as a bright reflection off the ocean surface (image 2 below). The flare occurred while TMI was scanning a broad swath across the Caribbean Sea, stretching across Guatamale, Belize, and Cuba. The radiation increased more than 100-fold during the flare and saturated the 11-GHz channels of TMI.

From the SOHO hotshot pages.

Image 1

[Image from the NASA/GSFC pages of the Scientific Visualization Studies.]

Image 2

[Image from the pages of the TMI remote sensing systems.]

Megaflare images at different photon energies

The Transition Region and Coronal Explorer (TRACE) observed its first "megaflare" on 2003 October 28. The main image, taken in the 195Å channel at 12:31 UT, shows the later phases of the flare, in which a rapidly cooling arcade of magnetic arches is visible, with material falling down back to the solar surface. The glowing arches are about 4 times the size of the Earth.

The 1st inset shows a false-color, blended image comparing the position of the brightly flaring region (green, as seen in the TRACE 1600Å passband at 11:22:24 UT) overlayed on a visible light image of the sunspot group (orange-red, TRACE WL image taken at 10:51:30). The flare arches (green) connect opposite magnetic polarities. The 2nd inset shows the average positions of the 2.2 MeV neutron-capture emission (red circles), which shows where energetic ions coming down from the coronal flare lose their energy near the solar surface. Also shown are contours of the hard X-ray (100 keV to 200 keV) bremsstrahlung generated by electron impact on the lower atmosphere (blue contours). Both emissions are related to brightest locations in the flare ribbons seen in EUV with TRACE (brightest where the diffraction crosses are seen), but they are displaced from each other by about 10,000 km.

Inset 1

Inset 2

[Image by Sam Krucker, SSL/ECB. Also available in postscript format]

X28 above the solar limb

The X28 flare observed by TRACE on 2003 November 4 at 08:51 UT in its 195Å channel. The ghostly flare emission is so bright that the solar disk (in the lower left of this image that was rotated by 90 degrees) is apparently completely dark in this exposure.

The line-drawing shows the X-ray light curve for the X28 flare, which increased the Sun's X-ray brightness (1-8Å) by a factor that was measured to be about 300; in fact, it was even stronger than that, but the GOES X-ray detectors saturated at the X17.4. The 2nd inset shows the RHESSI high-energy signals superimposed on a TRACE 195Å image. The thermal 10-20 keV X-ray emission is shown in contours (levels are 1,10,20,30,40,50,60,70,80,90 %). The green line gives the optical limb of the Sun. X-ray emitting hot loops are seen above already cooled down loops radiating in EUV.

Inset 1

Inset 2

[Image by Sam Krucker (SSL/UCB); also available in postscript format]

Cooling arcade

At 22:34 UT, almost three hours after the peak of the X28 flare on 2003 November 4, TRACE observed this arcade of cooling loops in its 195Å channel. This arcade of loops was part of the disrupted magnetic field during the early eruptive phase of the flare, and the heat deposited by the flare caused the loops to fill with hot gases. Now, these are cooling and raining down back to the solar surface.

CME and particle radiation.

The X28 flare on 2003 November 4 was associated with this coronal mass ejection (CME). This CME was the fastest observed to date, moving from the Sun at 10 million kilometers per hour. The picture was taken with the Large Angle and Spectrometric Coronagraph (LASCO) C3 instrument. The disk in the center of the image blocks the Sun's direct light so that the much fainter features high in the solar corona can be seen; the circle within the disk shows the size of the Sun.

The composite inset image sequence shows the CME at four different times. The CME expands in the field of view as it approaches the SOHO spacecraft because it was directed toward SOHO and the Earth. The many white spots in two of the images are caused by impacts of high-speed flare particles on the camera. LASCO instrument. These electrically charged particles, moving at a considerable fraction of the speed of light, has the potential to disrupt spacecraft electronics.

[From a NASA/GSFC top story.]


[Image from a NASA/GSFC top story.]

'Listening' to an eruption

On 2003 November 4, the Sun produced the fastest coronal mass ejection (CME) yet observed out of active region 10486 located near the southwest limb of the Sun. The image shows a composite made up of the extreme ultraviolet image of the Sun observed by SOHO/EIT (center; green), the inner coronagraph image (red; SOHO/LASCO), and the outer coronagraph image (blue; SOHO/LASCO). The inset shows the radio emission generated by the particles associated with the CME observed by the WAVES instrument on the NASA WIND satellite; it shows the frequencies drifting from around 10 Mhz to 1 Mhz over the period of an hour, which reflects the CME moving outward from the Sun into regions of rapidly weakening magnetic field.

[Image from a NASA/GSFC top story.]


The large flares in October and November of 2003 perturbed the Earth's outer atmosphere in several different ways. The X-ray emission, for example, affected the Earth's ionosphere so much that communications were difficult for some air traffic controllers, mountain climbers on Mount Everest, and for such unusual users as a group of rowing teams on the Atlantic Ocean. When the CME-related particles reached the Earth, they initiated a magnetic storm started early on the 2003 October 29. This storm produced unusually bright auroras. These auroral images were taken by the wideband Far Ultraviolet Camera onboard the NASA IMAGE spacecraft. The sun is located essentially behind the spacecraft for these images, so some of these auroras are superimposed on the fully sunlit Earth atmosphere.

[Image from Steve Mende (SSL/UCB); full-resolution version]

Radiation in the auroral oval

These two artificial images are derived from measurements by particle detectors on the NOAA/POES satellite in low-Earth orbit. The inset image shows the particle fluxes near their lowest levels, well before the period of high solar acitivity. When the strong coronal mass ejections sweep past the Earth, the particle fluxes increase dramatically over the polar caps, as they are carried towards the Earth guided by its magnetic field, here shown projected onto a model Earth. At times of very high particle fluxes, such as in the October/November 2003 period, air traffic control may redirect flights with flightpaths at latitudes above 35 degrees. They will particularly redirect polar flights that reach over 82 degrees north, not only to avoid the high radiation doses, but also to avoid the associated communications problems at VHF and HF frequencies. Such redirection costs a lot of extra fuel, which in turn means the planes can carry less freight, often adding up to tens of tons of denied freight per flight.

[Images from the NASA/GSFC Scientific Visualization Studio.]

Auroras from space and Earth

These pictures, taken with a spacecraft from the Air Force Defense Meteorological Satellite Program (DMSP), show the aurora borealis on 2003 October 29. These northern lights reach down into Scandinavia, the U.K., and the northern United States. These phenomena occur when strong coronal mass ejections collide with the Earth's magnetic field, causing geomagnetic storms. The inset shows the northern lights that day as seen from Ontario, Canada.

[Images from a Danish website, the NGST 'Featured picture' pages, and or the 'image of the day' from www.space.com.]


[Images from the web site of Lauri Kangas; the righthand image was color enhanced.]

Far out

The large flares on 2003 October 28 and November 4 emitted strong radio emission that was detected not only by observatories near and on Earth, but also by the Cassini spacecraft en route to Saturn. Such emission is excited as very energetic flare electrons that move through the solar wind. As the particles move through ever weaker field at greater distances from the Sun, the characteristic frequency shifts from high to low, causing the characteristic C-shape in the spectrogram images (called type III bursts).

The coronal mass ejections of the October-November 2003 period also reached far into the outer reaches of the solar system, thrown from the rotating Sun in directions that covered more than half the solar system. One of the CMEs passing by Mars knocked out the MARIE instrument on the orbiting Mars Odyssey spacecraft. Another CME was detected by the second-most distant man-made observatory, the Voyager 2 spacecraft that is now at 7 billion miles (11 billion kilometers) from the Sun; that coronal mass ejection overtook the Voyager 2 on 2004 April 28, 6 months after the event on the Sun. That CME never reached Voyager 1, at almost 9 billion miles (14.5 billion km) from the Sun. But because the Voyagers are travelling in rather different directions (see 2nd inset), the mass ejection observed by Voyager 2 likely simply missed Voyager 1.

[Main image from a NASA/GSFC top story.]

Inset 1

From the Cassini RPWS (Radio and Plasma Wave Science) pages, which also contains audio animations of the Type III radio bursts.

Inset 2

[The trajectories of the Voyager spacecraft from heavens-above.com.]

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.

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


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