Skywatchers around the world's Northern Hemisphere, who were treated to spectacular auroras last week, could get lucky again Monday night or Tuesday night, the result of another major solar flare over the weekend.
Though it was not pointed straight at Earth, Saturday's eruption of charged particles from the sun's surface was even stronger than the Aug. 1 solar flare, which was assigned to C-class status based on the brightness of its X-ray emissions. The flare could boost the northern lights displays this week for skywatchers at northern latitudes.
The latest flare has been given M-class status, the second most-intense category (after X-class). M-class flares are capable of causing radio interference around the Earth's poles.
Even though the Aug. 1 eruption wasn't powerful enough to have many noticeable effects on Earth, it caused a show of colors that satisfied those northerners who kept an eye on the night sky.
"I saw them as soon as the sun went down, and as I kept watching, the structure and the color turned completely mind-blowing," Gunjan Sinha, from Saskatchewan, Canada, told SPACE.com in an e-mail. "It never gets old watching them dancing with vibrant green color and also sometimes blue and red glow mixed with it." [See Sinha's stunning aurora photo.]
Solor flares, or coronal mass ejections, are eruptions of plasma and ionized atoms into space. As these atoms reach Earth, solar particles stream down the planet's magnetic field lines toward the poles.
In the process, the charged particles collide with atoms of nitrogen and oxygen in the atmosphere, creating impressive aurora light shows in the process.
"The actual experience itself was terrific," said Colin Chatfield, also of Saskatchewan, who snapped photos of the auroras. "It was a wonderful show the other night, and I'm glad that it wasn't clouded over like has been the case for much of the night-sky events this year."
Derek Weston, an avid aurora observer, was vacationing in St. Germain, Wis., when he caught the northern lights.
"Looking north, I could see what appeared to be a faint band of brightness on the horizon," Weston told SPACE.com, but after about an hour and a half, he said, "things really picked up. Now the green glow to the north had grown vertically, and on top of that vertical development we had rays going -? those are the pinks and purples you see."
An extreme ultraviolent photo released by NASA's Solar Dynamics Observatory showed the sun in mid-eruption. SDO, which was launched in February, captures high-definition views of the sun at a variety of wavelengths.
The interaction of the solar particles with Earth's magnetic field has the potential to create geomagnetic storms, or disturbances in the planet's magnetosphere. The Aug. 1 flare created a strong geomagnetic storm that lasted nearly 12 hours, NASA officials said in a statement.
Intense solar storms are capable of causing disturbances to space-based assets such as satellites, as well as to electronic infrastructure on Earth.?
The sun's activity usually ebbs and flows on a fairly predictable cycle. Typically, a cycle lasts about 11 years, taking roughly 5.5 years to move from a solar minimum, a period of time when there are few sunspots, to peak at the solar maximum, during which sunspot activity is amplified.
The last solar maximum occurred in 2001. The latest minimum was particularly weak and long- lasting. The most recent solar eruption is one of the first signs that the sun is ramping up activity and heading toward another maximum.
- Gallery - Amazing Auroras of 2010, Sun Storms
- Video of the Aug. 1 Sun Eruption
- Solar Tsunami Revealed in New Photo