Enhanced Technique for Tracking Solar Storms All the Way From Sun to Earth

Heliophysicists announced today that new data processing techniques have enabled them to track solar storms from their origin in the Sun’s fiery corona all the way to impact with the Earth in unprecedented detail. “For the first time we’ve been able to image a coronal mass ejection all the way through its entire life cycle, from inside the solar corona until it reaches Earth,” said Craig DeForest, speaking at a NASA press briefing. DeForest is the lead author paper published in the Astrophysical Journal.

CMEs and the solar wind evolve and change during the trip from the Sun to Earth – and some solar storms slow down and others speed up by the time they reach our planet.

Using new data processing techniques on existing data, and the five cameras from spacecraft, primarily the two STEREO spacecraft, the scientists can now identify which part of the CME came from Sun and which parts were swept up from the solar wind in its path.

STEREO has been able to track solar storms in their entirety before, but a new “data mining” technique allows for greater detail to be extracted

This new look helps resolve a 40-year mystery about the structure of the structures that cause space weather, and how the structures that impact the Earth relate to the corresponding structures in the solar corona.

This will help solar storm forecasters better predict storms that might arrive at Earth, since they now have a better understanding of how these storms evolve and grow.

“We now have a new understanding of how these events happen and that feeds into our forecasts,” said Alysha Reinard, research scientist, National Oceanic and Atmospheric Administration and the University of Colorado, Boulder. “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.”

The STEREO spacecraft have “heliospheric imager” cameras that monitor the sky at large angles from the Sun, but the starfield and galaxy are 1,000 times brighter than the faint rays of sunlight reflected by free-floating electron clouds inside CMEs and the solar wind; this has made direct imaging of these important structures difficult or impossible, and limited understanding of the connection between space storms and the coronal structures that cause them.

Newly released imagery reveals detailed features in a large geoeffective CME in late 2008, connecting the original magnetized structure in the Sun’s corona, and showing it in its entirety until it impacted the Earth three days later. At the time the data were collected, in late 2008, STEREO-A was nearly 45 degrees ahead of the Earth in its orbit, affording a very clear view of the Earth-Sun line.

When these clouds in CMEs leave the sun, they are bright and easy to see. However, visibility is quickly reduced, as the clouds expand into the void. The clouds are about one thousand times fainter than the Milky Way, which makes direct imaging of them difficult. That also has limited our understanding of the connection between solar storms and the coronal structures that cause them.

“Separating these faint signals from the star field behind them proved especially challenging, but it paid off,” said DeForest. “We have been drawing pictures of structures like these for several decades. Now that we can see them so far from the Sun, we find there is still a lot to learn.”

Watch another video of the 2008 solar storm hitting Earth.

See more videos from STEREO

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