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Solar storm ends years of tranquility

1/25/2012
A solar flare captured on January 23, 2012 [Credit: NASA's Solar Dynamics Observatory]
This image shows a solar flare as observed by the Atmospheric Imaging Assembly on NASA’s Solar Dynamics Observatory (SDO) at 04:12 Universal Time (Greenwich Time) on January 23, 2012. The solar surface brightened noticeably as gas was superheated and magnetically supercharged. You can see a stream of solar material flowing off into space above the hot spot, likely solar protons and a coronal mass ejection (CME).

The corona is the Sun's outer atmospheric layer. Solar flares occur in the neighborhood of sunspots at solar altitudes near this layer. The most distinguishing feature of solar flares is bright emission from long ribbons on the solar disk. Solar flares produce sudden bursts of energetic particles and high-energy radiation that persist for minutes to hours and travel at or near the speed of light. The energy that drives both solar flares and CMEs is believed to come from the interplay between the electrically charged gas in the solar atmosphere and the Sun's local magnetic field at the site of the event. Magnetic energy is converted to that of particle acceleration and heat.

NASA measured the high-latitude solar flare on January 23 as M8.7 in intensity, just below the most intense “X class” of flares. The eruption sent a stream of fast-moving, highly energetic protons toward Earth, provoking the most intense solar energetic particle storm since 2003. Spacecraft observed the CME with an initial speed of more than 2,000 kilometers (1,400 miles) per second. It collided with Earth's magnetic field a little after 10 AM Eastern Time on January 24.

Solar flares and CMEs can affect satellite operations and short-wave radio communications, and can pose some risks to astronauts, but cannot harm humans on Earth. They can provide a small dose of radiation to passengers on high-latitude flights. They can also bring auroras to high-latitude skies.

According to NASA, the storm was impressive by recent standards, but nowhere near the maximum intensities often generated at the height of the solar cycle. “I would expect that we will see more storms like this one or even bigger as we get closer to solar maximum,” said Michael Hesse, chief of heliophysics at NASA’s Goddard Space Flight Center.
For Further Study
SunSolar activitySun-climate connectionsSolar magnetic fieldSolar storms

Related Web Sites:
NASA's Solar Dynamics Observatory
Solar Flares: What Does It Take to Be X-Class?
Space Weather Prediction Center
The Sun-Earth Connection FAQ


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