Fastest Coronal Mass Ejection Observed By STEREO
August 14, 2012

STEREO Captures Fastest Coronal Mass Ejection To Date

[ Watch the Video: STEREO Captures Fastest CME to Date ]

Lee Rannals for - Your Universe Online

NASA's STEREO spacecraft has observed the fastest coronal mass ejection (CME) ever seen on the Sun.

The Solar TErrestrial RElations Observatory (STEREO) clocked the massive eruption traveling between 1,800 and 2,000 miles per second as it ejected from the sun.

NASA said this was the fastest CME ever observed by STEREO, which launched back in 2006.

"Between 1,800 and 2,200 miles per second puts it without question as one of the top five CMEs ever measured by any spacecraft," solar scientist Alex Young at Goddard said in a prepared statement. "And if it's at the top of that velocity range it's probably the fastest."

The STEREO mission utilizes two spacecraft with orbits that give them views of the sun that cannot be had from Earth.

By watching the Sun from all sides, scientists have a better understanding of how events transpire on our local star.

Scientists combined data from both STEREO and the European Space Agency and NASA's Solar Heliospheric Observatory (SOHO). Scientists can combine data from both missions to get a better grasp of the velocities they measured.

Rebekah Evans, a space scientist working at Goddard's Space Weather Lab, says that the team categorizes CMEs for their research in terms of their speed. The fastest CMEs are labeled "ER" for Extremely Rare.

"Seeing a CME this fast, really is so unusual," Evans said. "And now we have this great chance to study this powerful space weather, to better understand what causes these great explosions, and to improve our models to incorporate what happens during events as rare as these."

STEREO is able to observe the speed of the CME as it bursts from the sun, and provide even more data about 17 hours later as the CME physically swept by.

The spacecraft has instruments to measure the magnetic field strength, which in the case of the July 23 CME was four times as strong as the most common CMEs.

When a CME with a strong magnetic field arrives at Earth, it causes a geomagnetic storm, which disrupts Earth's own magnetic environment.  NASA says that this could potentially affect satellite operations or power grids.

"We measure magnetic fields in 'Tesla' and this CME was 80 nanoTesla," Antti Pulkkinen, who is also a space weather scientist at Goddard, said. "This magnetic field is substantially larger even than the CMEs that caused large geomagnetic storms near Earth in October 2003. We call those storms the Halloween storms and scientists still study them to this day."

Evans said that all of this solar activity was produced by a specific active region that NASA's space weather scientists had been watching for three weeks before the eruption on July 23.

"That active region was called AR 1520, and it produced four fairly fast CME's in Earth's direction before it rotated out of sight off the right limb of the sun," Evans said in a press release. "So even though the region had released multiple CMEs and even had an X-class flare, its strength kept increasing over time to eventually produce this giant explosion. To try to understand how that change happens makes for very exciting research."

STEREO is one of several missions that keep a constant eye on the sun. In the next year, the sun will be reaching "solar maximum," offering STEREO a once in 11 year chance to get a lot of observations in.