Observations from NASA’s Solar Dynamics Observatory, or SDO, have enabled scientists to confirm the existence of giant flows of gases and plasma moving heat from the sun’s interior to its surface.
The findings end 45 years of speculation about the “giant convection cells” and advance understanding of the formation of sunspot activity that causes space weather events, which can impact power grids and disrupt telecommunications infrastructure on Earth.
“The key to this discovery was that we were able to get continuous observations that are only available from space,” said Dr. David Hathaway, an astrophysicist at NASA’s Marshall Space Flight Center in Huntsville, Ala. “We may be able to look at these flows and identify areas where new sunspots are going to emerge, before we see them on the sun’s surface.”
Rising gases and plasma carry heat generated by nuclear reactions in the sun’s core to the surface by convective motion long observed in the rapid movement of small, short-lived cells of solar material. In 1968, researchers proposed the existence of “giant convection cells” made up of these smaller groups.
In a paper published today in the journal Science, Hathaway and his co-authors describe how data from the Helioseismic and Magnetic Imager (HMI) instrument on SDO made it possible to track the movement of gases and plasma within the giant cells, which can be up to 15 times the diameter of Earth and can last through multiple 27-day solar rotations.
The existence of the giant cells may also help explain why gases and material at the sun’s equator rotate about 30percent faster than at the poles, a key part of the origins of the sunspot cycle. The movement within the giant cells can cause flows of material moving toward the equator to move in the direction of rotation, keeping the sun spinning more quickly around its equator, and flows away from the equator to move in the opposite direction. These giant cells ultimately help drive the 11-year solar cycle and are likely to help highly magnetic active regions rise to the solar surface.
SDO is the first mission of NASA’s Living with a Star Program. The program’s goal is to develop the scientific understanding necessary to address those aspects of the sun-Earth system that directly affect our lives and society.
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Marshall Space Flight Center, Huntsville, Ala.