DO and STEREO spot something new on the Sun
Baku, April 13 (AZERTAC). The discovery of coronal cells has already increased scientists’ knowledge of the magnetic structure of the solar corona.
One day in the fall of 2011, Neil Sheeley, a solar scientist at the Naval Research Laboratory in Washington, D.C., did what he always does — look through the daily images of the Sun from NASA's Solar Dynamics Observatory (SDO).
But on this day, he saw something he'd never noticed before — a pattern of cells with bright centers and dark boundaries occurring in the Sun's atmosphere, the corona. These cells looked somewhat like a cell pattern that occurs on the Sun's surface — similar to the bubbles that rise to the top of boiling water — but it was a surprise to find this pattern higher up in the corona, which is normally dominated by bright loops and dark coronal holes.
Sheeley discussed the images with his Naval Research Laboratory colleague Harry Warren, and together they set out to learn more about the cells. Their search included observations from a fleet of NASA spacecraft called the Heliophysics System Observatory that provided separate viewpoints from different places around the Sun.
The coronal cells occur in areas between coronal holes — colder and less dense areas of the corona seen as dark regions in images — and "filament channels," which mark the boundaries between sections of upward-pointing magnetic fields and downward-pointing ones. Understanding how these cells evolve can provide clues as to the changing magnetic fields at the boundaries of coronal holes and how they affect the steady emission of solar material known as the solar wind streaming from these holes.
"We think the coronal cells look like flames shooting up, like candles on a birthday cake," said Sheeley. "When you see them from the side, they look like flames. When you look at them straight down, they look like cells. And we had a great way of checking this out because we could look at them from the top and from the side at the same time using observations from SDO, STEREO-A, and STEREO-B."
The discovery of coronal cells has already increased astronomers’ knowledge of the magnetic structure of the Sun's corona. In the future, studies of the evolution of coronal cells may improve scientists' understanding of the magnetic changes at coronal-hole boundaries and their effects on the solar wind and Earth's space weather.
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