We finally know why Sun's outer atmosphere is so hot
What's the story
In a groundbreaking discovery, scientists have found elusive small-scale torsional Alfven waves in the Sun's corona. The breakthrough was made using data from the world's most powerful solar telescope, the Daniel K. Inouye Solar Telescope in Hawaii. The finding could finally explain one of the biggest mysteries of our star: how its outer atmosphere reaches millions of degrees when its surface temperature is only around 5,500 degree Celsius.
Wave discovery
End of a long search for these waves
Alfven waves, named after Nobel Prize winner Hannes Alfven who predicted their existence in 1942, are magnetic disturbances that can carry energy via plasma. While larger versions of these waves have been observed before, this is the first time that smaller twisting types have been directly observed. Professor Richard Morton from Northumbria University led the research and said this discovery ends a long search for these waves dating back to the 1940s.
Telescope capabilities
Breakthrough made possible by advanced coronal instrument
The breakthrough was possible by the unique capabilities of Daniel K. Inouye Solar Telescope's Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP), an advanced coronal instrument. This spectrometer can witness incredibly fine details in the corona and is highly sensitive to changes in plasma movement. The telescope itself, with a 4m-wide mirror, represents two decades of international planning, with Northumbria University playing a crucial role in its development as part of a UK consortium that designed cameras for the telescope's Visible Broadband Imager.
Research breakthrough
New analytical techniques developed
Professor Morton developed new analytical techniques to separate different types of wave motion in the data. He observed the movement of iron heated to 1.6 million degrees Celsius, and discovered that swaying motions dominate plasma movement in the Sun's corona. These mask torsional motions, so he had to develop a way of removing the swaying to find twisting. This led to his discovery of these elusive small-scale torsional Alfven waves.
Wave implications
Implications for understanding the Sun's heating mystery
The discovery of these waves has major implications for understanding how the Sun operates. The corona, the Sun's outermost layer visible during solar eclipses, is heated to temperatures exceeding one million degrees Celsius. This heat accelerates the plasma away from the Sun as solar wind that fills our entire solar system. Alfven waves may also be the source of "magnetic switchbacks," the significant carriers of energy in the solar wind observed by NASA's Parker Solar Probe.