Researchers have seen for the first time the inner workings of coronal mass ejections, or CMEs, from its leaving the surface of the sun to its engulfing the Earth.
CMEs are billion-ton clouds of solar plasma launched by the same explosions that spark solar flares. When these explosions sweep past Earth, they can cause auroras, radiation storms, and in extreme cases, power outages, according to NASA.
Tracking these clouds and predicting their arrival is an important part of space weather forecasting. And, the forecasts for space weather could greatly improve now that researchers have unveiled new storm-tracking techniques, according to the space agency.
The movies shown on Thursday identified the arrival time of the CME and its mass. From the brightness of the cloud, researchers can accurately calculate the gas density. Though the event happened in 2008, NASA said their results for the event agreed with actual in situ measurements at the few percent level.
When this technique is applied to future storms, forecasters will be able to estimate its impact with greater confidence, according to NASA.
We have seen CMEs before, but never quite like this, said Lika Guhathakurta, program scientist for the STEREO mission at NASA headquarters, in a statement. STEREO-A has given us a new view of solar storms.
STEREO-A is one of two spacecrafts launched in 2006 to observe solar activity from widely-spaced locations.
Researchers say when the storm occurred, STEREO-A was more than 65 million miles from Earth, taking in the big picture view other spacecraft in Earth's orbit lack.
When CMEs first leave the sun, they are bright and easy to see. However, visibility is quickly decreased as the clouds expand into the void.
By the time a typical CME crosses the orbit of Venus, it's a billion times paler than the surface of the full Moon, and more than a thousand times fainter than the Milky Way, NASA said. CMEs that reach Earth are almost as gossamer as vacuum itself and correspondingly transparent.
Pulling these faint clouds out of the confusion of starlight and interplanetary dust has been an enormous challenge, says Craig DeForest of the Southwest Researcher Institute in Boulder, Colo., in a statement.
It took DeForest's team three years to learn how to do that, as they have been working on Thursday's footage since 2008. Their technique will now be applied on a regular basis, NASA said.
The movie sent chills down my spine, DeForest says. It shows a CME swelling into an enormous wall of plasma and then washing over the tiny blue speck of Earth where we live. I felt very small.
Alysha Reinard of NOAA's Space Weather Prediction Center, says there are benefits to space weather forecasting. She until quite recently, spacecraft could see CMEs only when they were still quite close to the sun.
And, by calculating a CME's speed during this brief period, Reinard says researchers we were able to estimate when it would reach Earth.
After the first few hours, however, the CME would leave this field of view and after that we were 'in the dark' about its progress, she says. The ability to track a cloud continuously from the Sun to Earth is a big improvement. In the past, our very best predictions of CME arrival times had uncertainties of plus or minus 4 hours. The kind of movies we've seen today could significantly reduce the error bars.
STEREO Tracks Solar Storms From Sun To Earth: NASA's STEREO spacecraft and new data processing techniques have succeeded in tracking space weather events from their origin in the sun's corona to impact with the Earth, resolving a 40-year mystery about the structure of the structures that cause space weather: how the structures that impact the Earth relate to the corresponding structures in the solar corona.