New Insights into Solar Corona Heating
A groundbreaking study published in the journal “Nature Astronomy” on October 24 has revealed significant findings about why the solar corona reaches temperatures of millions of degrees, while the surface of the sun remains around 5,500 degrees Celsius. This discovery highlights how Alfvén waves could be key to understanding this phenomenon.
Understanding Alfvén Waves and Their Role
Alfvén waves are magnetic oscillations that travel through plasma, first predicted in 1942 by Nobel laureate Hannes Alfvén. Larger versions of these waves have been observed before and are often linked to solar flares. However, the new discovery indicates that scientists have, for the first time, detected evidence of smaller and more sustainable versions of these waves, which may provide continuous energy to the sun.
The study was led by Professor Richard Morton from Northumbria University, who noted that this discovery concludes a long search for these waves that began in the 1940s. Scientists were able to directly observe the twisting motions that warp magnetic field lines in the corona.
Technological Advances with the Inouye Solar Telescope
This discovery was made possible by the Daniel K. Inouye Solar Telescope, particularly the Cryogenic Near-Infrared Spectropolarimeter (Cryo-NIRSP), the most advanced tool for studying the solar corona. This instrument can reveal fine structures in the solar atmosphere and measure even the smallest plasma movements.
The telescope features a four-meter mirror, four times larger than any previous solar telescope, making it the most powerful facility of its kind. Its construction required over twenty years of global collaboration, with Northumbria University contributing by designing cameras for the telescope’s visible broadband imager.
Tracking Superheated Iron in the Corona
Professor Morton was granted observation time while the telescope was still in its testing phase. Using the Cryo-NIRSP, his team tracked the movement of iron in the corona, which was heated to an astonishing temperature of 1.6 million degrees Celsius.
The primary method for identifying elusive twisting waves came from new data analysis techniques developed by Morton. As he explains, “Swaying motions dominate plasma movement in the solar corona, masking the twisting motions, so I had to develop a method to remove the swaying to reveal the twists.”
Unlocking the Secrets of Solar Heat and Corona Energy
This discovery provides new insights into how the sun’s atmosphere operates. The corona, visible during a total solar eclipse, can reach temperatures exceeding a million degrees Celsius, sufficient to propel charged particles outward as solar wind, filling our solar system.
The research involved scientists from Peking University (China), KU Leuven (Belgium), Queen Mary University of London, the Chinese Academy of Sciences, as well as the National Solar Observatory in Hawaii and Colorado, reflecting a broad international effort.
Understanding how Alfvén waves behave is practically important for predicting space weather, as solar wind carries magnetic disturbances that can interfere with GPS systems, satellites, and power grids on Earth. These new waves might also explain “magnetic switchbacks,” bursts of energy in the solar wind recently discovered by NASA’s Parker Solar Probe.
Conclusion
This discovery is a significant achievement in solar astronomy, opening doors for further research into how these waves propagate and distribute energy in the solar corona. The Daniel K. Inouye Solar Telescope and the Cryo-NIRSP offer high-quality spectra, paving the way for new studies in wave physics in the solar atmosphere. This research is supported by UK Research and Innovation Future Leaders Fellowships, the National Natural Science Foundation of China, and the European Union’s Horizon Europe program.