by Clara Moskowitz

SPACE.com Senior Writer
09 August 2011

from Space Website

This still from a video taken by NASA's Solar Dynamics Observatory

shows the August 8, 2011 solar flare as it appeared in the ultraviolet range of the light spectrum.

The flare registered as an X6.9 class sun storm, the largest of the Solar Cycle 24.
CREDIT: NASA/SDO/GSFC
 

An extremely powerful solar flare, the largest in over four years, rocked the sun early Tuesday (August 9), but is unlikely to wreak any serious havoc here on Earth, scientists say.

"It was a big flare," said Joe Kunches, a space scientist with the National Oceanic and Atmospheric Administration (NOAA)'s Space Weather Prediction Center.

 

"We lucked out because the site of the eruption at the sun was not facing the Earth, so we will probably feel no ill effects."

Today's solar flare began at 3:48 a.m. EDT (07:48 GMT), and was rated a class X6.9 on the three-class scale scientists use to measure the strength of solar flares.

The strongest type of solar eruption is class X, while class C represents the weakest and class M flares are medium-strength events. (Sun's Wrath - Worst Solar Storms in History)

The flare is the largest one yet in the sun's current cycle, which began in 2008 and is expected to last until around 2020.

Solar activity waxes and wanes over an 11-year sun weather cycle, with the star currently heading toward a solar maximum in 2013.

"This flare had a GOES X-ray magnitude of X6.9, meaning it was more than 3 times larger than the previous largest flare of this solar cycle - the X2.2 that occurred on Feb 15, 2011," scientists with NASA's Solar Dynamics Observatory, a space observatory that monitors the sun, wrote in an update.

Before the February 15 storm, the largest recent solar flare occurred in December 2006, when an X9-class solar storm erupted from the sun.

Solar flares occur when magnetic field lines on the sun get tangled up into knots, building potential energy until they reach a tipping point. Then, that energy is converted into heat, light and the motion of charged particles.

While all X-class solar eruptions are major events, they pose the greatest threat to Earth when they are aimed directly at the planet. During those events the sun often releases a cloud of plasma called a coronal mass ejection into space, and sometimes toward Earth.

This ejection hurls charged particles that can damage satellites, endanger astronauts in orbit, and interfere with power systems, communications and other infrastructure on the planet.
 

Major Solar Flare

August 9, 2011
 

Today's solar flare, and resulting coronal mass ejection (CME) was not aimed at us, however.

Stunning Photos of Solar Flares & Sun Storms

Sun's Twisting Plasma Tentacle. Credit: NASA/SDO/GSFC. NASA's Solar Dynamics Observatory spacecraft captured this eruption from March 19, 2011 as a prominence became unstable and blasted into space with a distinct twisting motion.	Monster Prominence. Credit: NASA/SDO. NASA's Solar Dynamics Observatory captured this view of a powerful M3.6 Class solar flare on Feb. 24, 2011 during a 90-minute sun storm. NASA scientists called the display a "monster prominence" that kicked up a huge plasma wave.	Blazin'. Credit: TRACE Project, NASA. This ultraviolet image of the sun shows large sunspot group AR 9169 as the bright area near the horizon. The relatively cool dark regions have temperatures of thousands of degrees Celsius, in contrast to the bright glowing gas flowing around the sunspots, which have a temperature of over one million degrees Celsius. Large sunspot group AR 9169 moved across the sun during September 2000.
Sun's Active Region 1158 Solar Flare Credit: NASA/SDO/GFSC An X2.2 flare erupted from the sun's active region 1158 (at lower right) at about 0150 UT or 8:50 pm ET on Feb. 14, 2011.	Bastille Day Solar Flare Credit: NASA The "Bastille Day" solar flare as seen by SOHO's EIT instrument in the 195 Å emission line.	Solar C7 Flare in Ultraviolet Credit: NASA/SDO The Solar Dynamics Observatory captured this video of the C7 flare of June 20, 2011 in extreme ultraviolet wavelength at 335 Å.

 

"Because of its position the CME is going to shoot out into space and not be Earth-directed, and we don’t expect any big geomagnetic storm with this," Kunches told SPACE.

 

"We did luck out. If this would have happened a week ago, who knows?"

However, some VLF and HF radio communications blackouts have been reported, according to Spaceweather, a website that monitors space weather events.

Whatever particles do head our way should reach us in a few days.

Video

August 9 Solar Flare Briefly Knocks Out HF Radio

"The cloud will probably miss Earth," SpaceWeather wrote. "At this time, however, we cannot rule out a glancing blow from the flank of the CME on or about August 11^th."

The plus side of such a collision is often unusually spectacular auroras, or Northern and Southern Lights, which occur when charged particles interact with Earth's magnetic field.