Enormous Magnetic Waves Bake Sun's Corona
Physicists have long questioned why the sun’s corona, or outer atmosphere, manages to generate so much heat. New research seems to have brought them one step closer to finding the answer.
The solar corona is visible during total an eclipse as the bright halo around the sun, and it reaches temperatures massively in excess of the sun’s surface.
The sun's surface is about 5,800 degrees Kelvin, or about 10,000 Fahrenheit. However, scientists measure the corona, which extends several times the radius of the sun into space, as much hotter; reaching temperatures of millions of degrees.
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Researchers from National Center for Atmospheric Research (NCAR) have now found evidence that suggests powerful magnetic field ripples, called Alfven waves, might be driving the solar wind and heating much of the corona.
Researchers are using NASA’s Solar Dynamics Observatory (SDO) to track the movement of the solar “seaweed”, and through this they are able to measure how much energy is carried by the Alfvén waves.
Scientists have found that magnetic oscillations carrying energy from the Sun's surface into its corona are far more vigorous than previously estimated.
Scott McIntosh, the study's lead author and a scientist at NCAR's High Altitude Observatory has announced in press release: "The new satellite observations are giving us a close look for the first time at how energy and mass move through the Sun's outer atmosphere.”
Alfven waves were only observed for the first time in 2007, when amplitudes of about 1,600 feet (0.5 kilometers) per second were witnessed. This was far too small to heat the corona to its high levels or to drive the solar winds being witnessed.
The new study, however, shows that Alfven waves are more than a hundred times more powerful than previously measured. Amplitudes of a massive 12 miles (20 km) per second were measured, which is enough to heat the Sun’s outer atmosphere to millions of degrees and drive the solar wind.
The waves can be seen through high-resolution images of the outer atmosphere, and shots show them causing high-speed jets of hot material, called spicules, to sway.
McIntosh said, “We now understand how hot mass can shoot upward from the solar interior, providing enough energy to maintain the corona at a million degrees and fire off particles into the high-speed solar wind. This new research will help us solve essential mysteries about how energy gets out of the Sun and into the solar system.
“Understanding solar processes advances our knowledge of Earth-Sun interactions, providing insights on how UV radiation generated by solar storms affects the Earth's upper atmosphere, stratospheric ozone and - potentially - global climate dynamics over both short and longer time scales.”
