NASA SDO: Spots Extra Energy in the Sun's Corona

These jets, known as spicules, were captured in an SDO image on April 25, 2010.

Combined with the energy from ripples in the magnetic field, they may contain enough energy to power the solar wind that streams from the sun toward Earth at 1.5 million miles per hour. Credit: NASA/SDO/AIA

Like giant strands of seaweed some 32,000 miles high, material shooting up from the sun sways back and forth with the atmosphere. In the ocean, it's moving water that pulls the seaweed along for a ride; in the sun's corona, magnetic field ripples called Alfvén waves cause the swaying.

For years these waves were too difficult to detect directly, but NASA's Solar Dynamics Observatory (SDO) is now able to track the movements of this solar "seaweed" and measure how much energy is carried by the Alfvén waves.

The research shows that the waves carry more energy than previously thought, and possibly enough to drive two solar phenomena whose causes remain points of debate: the intense heating of the corona to some 20 times hotter than the sun's surface and solar winds that blast up to 1.5 million miles per hour.

"SDO has amazing resolution so you can actually see individual waves," says Scott McIntosh at the National Center for Atmospheric Research in Boulder, Colo. "Now we can see that instead of these waves having about 1000th the energy needed as we previously thought, it has the equivalent of about 1100W light bulb for every 11 square feet of the sun's surface, which is enough to heat the sun's atmosphere and drive the solar wind."

McIntosh published his research in a Nature article appearing on July 28. Alfvén waves, he says, are actually fairly simple. They are waves that travel up and down a magnetic field line much the way a wave travels up and down a plucked string. The material surrounding the sun -- electrified gas called plasma – moves in concert with magnetic fields. SDO can see this material in motion and so can track the Alfvén waves.