Scientists discover elusive solar waves that could power the sun’s corona

Researchers have achieved a breakthrough in solar physics by providing the first direct evidence of small-scale torsional Alfvén waves in the sun’s corona—elusive magnetic waves that scientists have been searching for since the 1940s.

The discovery, published in Nature Astronomy, was made using unprecedented observations from the world’s most powerful solar telescope, the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope in Hawaii.

The findings could finally explain one of the sun’s greatest mysteries—how its outer atmosphere, the corona, reaches temperatures of millions of degrees while its surface is only around 5,500°C.

Alfvén waves, named after Nobel Prize winner Hannes Alfvén who predicted their existence in 1942, are magnetic disturbances that can carry energy through plasma.

Scientists have spotted larger, isolated versions of these waves before—normally related to solar flares. However, this is the first time that the small twisting type, which is present all the time and could power the sun, has been directly observed.

UKRI Future Leader Fellow Professor Richard Morton, a Professor within Northumbria University’s School of Engineering, Physics and Mathematics, led the research. He said, “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.”

The breakthrough was made possible by the unique capabilities of the Daniel K. Inouye Solar Telescope’s Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP), the most advanced coronal instrument of its kind. This cutting-edge spectrometer can see incredibly fine details in the corona and is highly sensitive to changes in the movement of plasma.

With its four-meter-wide mirror—four times larger than previous solar telescopes—the Daniel K. Inouye Solar Telescope, built and operated by the NSF National Solar Observatory, represents two decades of international planning and development.

Northumbria University has played a crucial role in its development as part of a UK consortium that designed cameras for the telescope’s Visible Broadband Imager, building on the University’s established reputation for observations of the solar atmosphere.

Professor Morton won time to use the telescope while it was still being tested and used the instrument to track the movement of iron, heated to 1.6 million degrees Celsius, in the corona.

The key breakthrough came from Professor Morton developing entirely new analytical techniques to separate different types of wave motion in the data. 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.”

While the more familiar ‘kink’ waves cause entire magnetic structures to sway back and forth and are visible in film captured of the sun, the newly detected torsional Alfvén waves cause a twisting motion that can only be detected through spectroscopic analysis—measuring how plasma moves toward and away from Earth, creating characteristic red and blue shifts on opposite sides of magnetic structures.

The discovery has profound implications for understanding how the sun works. The corona, the sun’s outermost atmosphere visible during solar eclipses, is heated to temperatures exceeding one million degrees Celsius—hot enough to accelerate plasma away from the sun as the solar wind that fills our entire solar system.

The research represents a major international collaboration, with co-authors from Peking University in China, KU Leuven in Belgium, Queen Mary University of London, the Chinese Academy of Sciences, and the NSF National Solar Observatory in Hawaii and Colorado.

Understanding these fundamental processes has practical importance for space weather prediction. The solar wind carries magnetic disturbances that can disrupt satellite communications, GPS systems, and power grids on Earth. Alfvén waves may also be the source of “magnetic switchbacks”—significant carriers of energy in the solar wind that have been observed 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.”

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.