Small Sunspot, Big Flare
February 7, 2000
-- This weekend a major solar flare erupted on the northeast
limb of the Sun at 1928 UT on February 5. According to data from
the NOAA Space Environment Center, it was one of the largest
and brightest optical flares of the current solar cycle.
Right: This image of the Sun was taken through a red "H-alpha" filter at the Holloman Air Force Base in New Mexico. The bright spot closest to the upper left corner is the solar flare.
The eruption was bright across the electromagnetic spectrum. It registered the maximum rating of "B" (for brilliant) on the 3-level scale of optical intensity for solar flares. At X-ray wavelengths the Earth-orbiting GOES 8 satellite also detected a bright surge that put the flare in the most powerful X-class. Large flares like this one can emit up to 1032 ergs of energy. This energy is ten million times greater than the energy released from a volcanic explosion. On the other hand, it is less than one-tenth of the total energy emitted by the Sun every second.
- The Earth's upper atmosphere becomes more ionized and expands.
- Long distance radio signals can be disrupted by the resulting change in the Earth's ionosphere.
- A satellite's orbit around the Earth can be disturbed by the enhanced drag on the satellite from the expanded atmosphere.
- Satellites' electronic components can be damaged.
Solar flares become more common during sunspot maximum. The current sunspot cycle is slated to peak in mid-2000, and remain high for at least a year.
|Parents and Educators: Please visit Thursday's Classroom for lesson plans and activities related to this story.|
Although the Feb. 5 solar flare was big and bright, it did
not come from a particularly impressive sunspot group. Active
region 8858, the site of the flare, covers just 200 millionths
of the solar disk. However, its magnetic field is complex, exhibiting
strong gradients that make it a likely site for flare activity.
Space weather forecasters expect the region to continue developing
in the coming days. If that happens, we could be in for more
Right The animation (left) is a three frame sequence of H-alpha images showing the progress of the flare over a two hour period. (Frame credits: Holloman Air Force Base, New Mexico) The still image (right) shows sunspot group 8858 a day later on January 6, 2000. (Credit: the Solar and Heliospheric Observatory). The two pictures are approximately to scale. For a full disk image of the sun on January 6, 2000, click on the still image of the sunspot group.
Just after the solar flare, the Solar and Heliospheric Observatory (SOHO) recorded a dramatic coronal mass ejection (CME) traveling approximately 500 kilometers per second away from the Sun. The ejected material did not appear to be headed for Earth. However, if this sunspot group produces more coronal mass ejections in the coming week, they could become Earth-directed as the active region rotates across the Sun's central meridian.
Left: This animation shows data obtained by SOHO's LASCO C2 coronagraph shortly after the onset of the February 5 solar flare. To view a more complete sequence of this coronal mass ejection click here. The C2 coronagraph is able to observe the Sun's corona between 1.1 and 3 solar radii. The CME was also seen by the C3 coronagraph, which has a wider view covering 3.5 to 30 solar radii. Click here for that animation.
Coronal mass ejections can carry up to 10 billion tons of plasma traveling at speeds as high as 2000 km/s. When they collide directly with Earth they can excite geomagnetic storms, which have been linked to satellite communication failures. In extreme cases, such storms can induce electric currents in the Earth and oceans that can interfere with or even damage electric power transmission equipment. Energetic particles and radiation from solar flares reach the Earth is just minutes. The slower-moving material from a coronal mass ejection usually takes days to reach our planet.
Solar Cinema - January 19, 2000 NASA Science News. Cool movies of a recent solar prominence.
Solar Smoke Rings - February 3, 2000 NASA Science News. As solar maximum approaches, the Sun is belching billions of tons of gas into interplanetary space.
Solar Flares - Learn more about solar flares and coronal mass ejections at this excellent web site from NASA/Goddard.
SpaceWeather.com -follow the latest events on the Sun
Coronal Mass Ejections -from the Marshall Space Flight Center
SOHO home page -real-time images, screen savers, and more