Researchers have made a major leap in solar physics by finding the first direct evidence of small-scale torsional Alfvén waves within the Sun’s corona. These elusive magnetic waves, first theorized in the 1940s, have long been suspected to play a key role in heating the Sun’s outer atmosphere.
The findings, published on October 24 in Nature Astronomy, were achieved using the powerful U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope in Hawaii. With this discovery, scientists may finally have an explanation for why the Sun’s outer layer, the corona, reaches millions of degrees while its surface remains around 5,500°C.
Understanding Alfvén Waves and Their Role
Alfvén waves are magnetic vibrations that move through plasma, first predicted in 1942 by Nobel laureate Hannes Alfvén. Larger versions of these waves have been seen before, often linked to solar flares. This new observation, however, marks the first time scientists have captured evidence of the smaller, constantly present twisting type that may provide continuous energy to the Sun.
UKRI Future Leader Fellow Professor Richard Morton of Northumbria University led the study. He explained, “This discovery ends a protracted search for these waves that has its origins in the 1940s. We’ve finally been able to directly observe these torsional motions twisting the magnetic field lines back and forth in the corona.”
A Technological Breakthrough with the Inouye Solar Telescope
The discovery was made possible by the Daniel K. Inouye Solar Telescope’s Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP), the most advanced instrument ever built to study the Sun’s corona. This instrument can detect extremely fine structures in the solar atmosphere and measure even the slightest motion of plasma.
The telescope’s four-meter mirror — four times larger than any previous solar telescope — makes it the most powerful facility of its kind. Operated by the NSF’s National Solar Observatory, it represents over twenty years of global collaboration. Northumbria University contributed through a UK consortium that designed cameras for the telescope’s Visible Broadband Imager, building on the institution’s strong background in solar research.
Tracking Superheated Iron in the Corona
Professor Morton was granted observing time while the telescope was still undergoing testing. Using Cryo-NIRSP, his team followed the movement of iron in the corona, heated to an extraordinary 1.6 million degrees Celsius.
The key to identifying the elusive twisting waves came from new data analysis methods developed by Morton. As he explains: “The movement of plasma in the sun’s corona is dominated by swaying motions. These mask the torsional motions, so I had to develop a way of removing the swaying to find the twisting.”
Unlike the more familiar “kink” waves that cause entire magnetic structures to sway and can be seen in solar videos, torsional Alfvén waves create a subtle twisting motion that can only be detected spectroscopically. This means scientists must measure how plasma shifts toward and away from Earth, producing telltale red and blue patterns on opposite sides of magnetic structures.
Unlocking the Secrets of Solar Heat and Energy
This discovery sheds new light on how the Sun’s atmosphere functions. The corona, visible during total solar eclipses, can exceed one million degrees Celsius — hot enough to propel charged particles outward as the solar wind that fills our solar system.
The research involved scientists from Peking University (China), KU Leuven (Belgium), Queen Mary University of London, the Chinese Academy of Sciences, and the NSF National Solar Observatory in Hawaii and Colorado, reflecting a broad international effort.
Understanding how Alfvén waves behave has practical significance for predicting space weather. The solar wind carries magnetic disturbances that can interfere with GPS, satellites, and power grids on Earth. These newly observed waves may also explain “magnetic switchbacks,” bursts of energy in the solar wind recently detected by NASA’s Parker Solar Probe.
“This research provides essential validation for the range of theoretical models that describe how Alfvén wave turbulence powers the solar atmosphere,” added Professor Morton. “Having direct observations finally allows us to test these models against reality.”
Future Research and Ongoing Discoveries
The team anticipates this discovery will spark further investigations into how these waves propagate and dissipate energy in the corona. The ability of the Daniel K. Inouye Solar Telescope’s Cryo-NIRSP instrument to provide high-quality spectra opens new possibilities for studying wave physics in the solar atmosphere.
The research was supported by UKRI Future Leaders Fellowships, the National Natural Science Foundation of China, and the European Union’s Horizon Europe programme.
This is the third paper Professor Morton has published this year in relation to his research into Alfvén waves. In April 2025 the paper High-frequency Coronal Alfvénic Waves Observed with DKIST/Cryo-NIRSPwas published in The Astrophysical Journal, followed by the paper On the Origins of Coronal Alfvénic Waves, published in June 2025 in The Astrophysical Journal Letters.