STEREO observes one of the fastest coronal mass ejections on record (w/ Video)

Aug 13, 2012
This image was captured by ESA and NASA’s Solar and Heliospheric Observatory (SOHO) on July 22, 2012 at 10:48 p.m. EDT. On the right side, a cloud of solar material ejects from the sun in one of the fastest coronal mass ejections (CMEs) ever measured. Credit: Credit: ESA&NASA/SOHO

On July 23, 2012, a massive cloud of solar material erupted off the sun's right side, zooming out into space, passing one of NASA's Solar TErrestrial RElations Observatory (STEREO) spacecraft along the way. Using the STEREO data, scientists at NASA's Goddard Space Flight Center in Greenbelt, Md. clocked this giant cloud, known as a coronal mass ejection, or CME, as traveling between 1,800 and 2,200 miles per second as it left the sun.

Conversations began to buzz and the emails to fly: this was the fastest CME ever observed by STEREO, which since its launch in 2006 has helped make CME speed measurements much more precise. Such an unusually strong bout of space weather gives scientists an opportunity to observe how these events affect the space around the , as well as to improve their understanding of what causes them.

"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," says solar scientist Alex Young at Goddard. "And if it's at the top of that velocity range it's probably the fastest."

The consists of two spacecraft with orbits that for most of their journey give them views of the sun that cannot be had from Earth. Watching the sun from all sides helps improve our understanding of how events around the sun are connected, as well as gives us glimpses of activity we might not otherwise see. On July 23, STEREO-A lay – from Earth's perspective -- to the right side and a little behind the sun, the perfect place for seeing this CME, which would otherwise have been hard to measure from Earth. The Solar Heliospheric Observatory (SOHO), an ESA and NASA mission, also observed the CME. It is the combination of observations from both missions that helps make scientists confident in the large velocities they measured for this event.

Measuring a CME at this speed, traveling in a direction safely away from Earth, represents a fantastic opportunity for researchers studying the sun's effects. Rebekah Evans is a space scientist working at

Goddard's Space Weather Lab, which works to improve models that could some day be used to improve predictions of space weather and its effects. She says that the team categorizes CMEs for their research in terms of their speed, with the fastest ones – such as this one -- labeled "ER" for Extremely Rare.

This video is not supported by your browser at this time.
This movie shows a coronal mass ejection (CME) on the sun from July 22, 2012 at 10 p.m. EDT until 2 a.m. July 23 as captured by NASA's Solar TErrestrial RElations Observatory-Ahead (STEREO-A). Because the CME headed in STEREO-A's direction, it appears like a giant halo around the sun. NOTE: This video loops three times. Credit: NASA/SDO

"Seeing a CME this fast, really is so unusual," says Evans. "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."

Orbiting the sun some 89,000,000 miles away, STEREO-A could observe the speed of the CME as it burst from the sun, and it provided even more data some 17 hours later as the CME physically swept by – having slowed down by then to about 750 miles per second. STEREO has instruments to measure the strength, which in this case was four times as strong as the most common CMEs. When a CME with strong magnetic fields arrives near Earth, it can cause something called a geomagnetic storm that disrupts Earth's own magnetic environment and can potentially affect satellite operations or in worst-case scenarios induce electric currents in the ground that can affect power grids.

"We measure magnetic fields in 'Tesla' and this CME was 80 nanoTesla," says Antti Pulkkinen, who is also a space weather scientist at Goddard. "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."

While large, this measurement of the magnetic field is still smaller than one of the greatest space weather events on record, the Carrington Event of 1859, during which the magnetic fields at Earth measured 110 nanoTesla.

When the CME passes over one of the , the instruments can also measure the direction in which the magnetic field points – a crucial data point since it is the southward pointing magnetic fields in a CME that travel in the opposite direction of Earth's own magnetic fields and thus can cause the most disruption. This CME traveled with an unusually large southward magnetic field of 40 nanoTesla that stayed steady for several hours.

The event also pushed a burst of fast protons out from the sun. The number of charged particles near STEREO jumped 100,000 times within an hour of the CME's start. When such bursts of solar particles invade Earth's magnetic field they are referred to as a solar radiation storm, and they can block high frequency radio communications as used, for example, by airline pilots. Like the CME, this solar energetic particle (SEP) event is also the most intense ever measured by STEREO. While the CME was not directed toward Earth, the SEP did – at a much lower intensity than at STEREO – affect Earth as well, offering scientists a chance to study how such events can widen so dramatically as they travel through space.

Evans points out that all of this solar activity was produced by a specific active region that 's space weather scientists had been watching for three weeks before the super fast 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," says Evans. "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 but one of several missions that observe the sun constantly, and the data is always interesting as there is much to be learned from observing the quiet sun as well as an active one. But the sun displays an activity cycle during which it gets more active approximately every 11 years as it heads toward what's called "solar maximum." The next solar maximum is currently predicted for 2013. We can expect more and more events until then, and each one will help scientists better understand the sun and how its effects can permeate the entire solar system.

Explore further: Observing the onset of a magnetic substorm

Related Stories

A 360 degree view of an X-class flare and a CME

Nov 08, 2011

(PhysOrg.com) -- The sun sent out two different kinds of solar activity last night in different directions. One was an X 1.9 class flare that burst out from an active region on the sun, numbered AR1339, which ...

New ways to measure magnetism around the sun

Jul 14, 2011

Those who study the sun face an unavoidable hurdle in their research – their observations must be done from afar. Relying on images and data collected from 90 million miles away, however, makes it tough ...

Scientists see solar outburst in exquisite detail

Apr 20, 2011

(PhysOrg.com) -- The largest disturbances to the Earth's geomagnetic environment occur when it is buffeted by solar material hurled in our direction by explosive changes in the Sun's atmosphere. These Coronal ...

Moderate Labor Day solar flare eruption

Sep 07, 2011

At 9:35 PM ET on September 5, 2011, the sun emitted an Earth-directed M5.3 class flare as measured by the GOES satellite. The flare erupted from a region of the sun that appears close to dead center from Earth's ...

Beautiful red Aurora

Oct 27, 2011

(PhysOrg.com) -- A coronal mass ejection (CME) shot off the sun late in the evening of October 21 and hit Earth on October 24 at about 2 PM ET. The CME caused strong magnetic field fluctuations near Earth's ...

Recommended for you

Observing the onset of a magnetic substorm

7 hours ago

Magnetic substorms, the disruptions in geomagnetic activity that cause brightening of aurora, may sometimes be driven by a different process than generally thought, a new study in the Journal of Geophysical Research: Space Ph ...

We are all made of stars

10 hours ago

Astronomers spend most of their time contemplating the universe, quite comfortable in the knowledge that we are just a speck among billions of planets, stars and galaxies. But last week, the Australian astronomical ...

ESA video: The ATV-5 Georges Lemaitre loading process

10 hours ago

This time-lapse video shows the ATV-5 Georges Lemaitre loading process and its integration on the Ariane 5 launcher before its transfer and launch to the International Space Station from Europe's Spaceport in Kourou, French ...

Titan's subsurface reservoirs modify methane rainfall

13 hours ago

(Phys.org) —The international Cassini mission has revealed hundreds of lakes and seas spread across the icy surface of Saturn's moon Titan, mostly in its polar regions. These lakes are filled not with water ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

GenesisNemesis
not rated yet Aug 13, 2012
Wish I could be that close to the Sun.
visual
not rated yet Aug 14, 2012
How does it lose so much speed? Its speed seems to have gone down by more than half, which means it lost more than 75% of its kinetic energy...

A quick approximate calculation shows that gravity can slow down an object that leaves the sun surface at slightly under 400 miles per second down to rest at 90 million miles away.

But due to the squared relationship between kinetic energy and velocity, an object moving 4 times faster at the sun surface, will lose only 1/16th of its kinetic energy for the same distance, a far cry from the 75% suggested by this article.

If it was moving at 1800 miles per second, gravity alone will only slow it down a measly 42 miles per second.

What is going on here?
HannesAlfven
1 / 5 (1) Aug 14, 2012
Re: "What is going on here?"

In the lab, we accelerate and decelerate charged particles with electric fields. But, not so much in astrophysics ...