Scientists have finally discovered theoretical torsional Alfvén waves within the Sun’s corona, concluding a search that began in the 1940s.
The U.S. National Science Foundation’s Daniel K. Inouye Solar Telescope in Hawaii facilitated the unprecedented discovery, as detailed in a new paper in Nature Astronomy. Researchers believe the observations will eventually explain how the Sun’s corona, at millions of degrees, reaches such extreme temperatures while its surface remains much cooler at 5,500 °C.
Alfvén Waves
Hannes Alfvén first predicted the plasma-transporting magnetic disturbances known as Alfvén waves in 1942. While larger isolated Alfvén waves have been captured in previous solar flare observations, this is the first time the continually present, small, twisting variety suspected to power the Sun has been seen directly.
“This discovery ends a protracted search for these waves that has its origins in the 1940s,” said lead author Professor Richard Morton of Northumbria University. “We’ve finally been able to directly observe these torsional motions twisting the magnetic field lines back and forth in the corona.”
Professor Morton made the discovery after winning a bid for time on the Daniel K. Inouye Solar Telescope, during which he was able to employ its Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP). The instrument was still in its testing phase while he made his observations, and as the most advanced coronal instrument of its kind, the Cryo-NIRSP can resolve extremely fine details in its observations, in addition to allowing the detection of plasma movements with great sensitivity.
Moving Plasmas
In his research, Morton focused on tracking the movement of iron through the corona, which under such conditions is heated to remarkable temperatures of close to 1.6 million degrees Celsius. In doing so, he developed a new technique to separate different types of wave motion in the data he collected.
“The movement of plasma in the sun’s corona is dominated by swaying motions,” Morton said. “These mask the torsional motions, so I had to develop a way of removing the swaying to find the twisting.”
“Kink” waves are a more well-observed phenomenon in past observations of the Sun, which play a role in influencing the back-and-forth sway of magnetic structures. However, the twisting motion of torsional Alfvén waves is only apparent under spectrographic analysis; as the plasma leaves the solar surface and recedes, it produces blue and red shifts on opposite sides of magnetic structures.
Understanding the Sun
Morton says the new data will provide significant insight into how the Sun’s corona operates. During solar eclipses, the one-million-degree plasmas create a fiery outline around the Moon. Such extreme temperatures are enough to thrust this plasma into space, where it becomes the solar wind and eventually reaches our planet.
Such space weather phenomena are a primary concern for humanity, as they can have significant effects on our technological infrastructure, especially as the number of systems in low Earth orbit grows. By understanding the fundamental processes at play, scientists hope to refine and improve space weather predictions. By doing so, experts can better mitigate threats to communications systems, GPS, and power grids, all of which are vulnerable to space weather.
“This research provides essential validation for the range of theoretical models that describe how Alfvén wave turbulence powers the solar atmosphere,” added Morton. “Having direct observations finally allows us to test these models against reality.”
With the Daniel K. Inouye Solar Telescope’s Cryo-NIRSP instrument, scientists have a valuable new tool to probe the mysteries of the Sun, providing the data required to push solar physics research. Morton’s team believes that future work will build on what they have accomplished to better understand how Alfvén waves propagate and dissipate energy into the corona, further expanding our knowledge of the Sun and its mysteries.
The paper, “Evidence for Small-scale Torsional Alfvén Waves in the Solar Corona,” appeared in Nature Astronomy on October 24, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.