An international research team has obtained the first direct evidence of small-scale torsional Alfvén waves in the solar corona using world-leading solar observation equipment. Published in Nature Astronomy, this breakthrough is expected to resolve the long-standing scientific puzzle of why the Sun's outer atmosphere is far hotter than its surface.

This groundbreaking discovery was made possible by the Daniel K. Inouye Solar Telescope in Hawaii, operated by the U.S. National Science Foundation. Equipped with a four-meter mirror, the telescope captured subtle twisting motions of magnetic fields in the corona using its cryogenic near-infrared spectropolarimeter. Lead researcher Professor Richard Morton from Northumbria University in the UK stated: "Our innovative analysis method successfully separated different types of wave signals, ultimately allowing us to directly observe these persistent Alfvén waves twisting magnetic field lines back and forth in the corona."

Scientists have been searching for Alfvén waves—capable of transferring energy through plasma in the form of magnetic disturbances—since the 1940s. The small-scale persistent oscillations discovered this time differ significantly from the isolated large-scale waves previously observed in solar flares. Professor Morton added: "This finding provides critical validation for theoretical models describing how Alfvén wave turbulence drives the solar atmosphere."

The research team developed specialized analysis techniques to isolate torsional motion signals from dominant swaying motions. By detecting characteristic redshifts and blueshifts on either side of magnetic structures through spectral analysis, the researchers ultimately confirmed the presence of Alfvén waves. This achievement will advance the in-depth exploration of coronal heating mechanisms and positively impact the refinement of space weather forecasting models.