A long-standing mystery about the sun’s atmosphere might finally be getting answers. For years, scientists have puzzled over why the sun’s outer layer, known as the corona, is much hotter than its surface. While the surface can reach millions of degrees, the corona sizzles at nearly 10,000°F (5,500°C).
Recent observations from the Daniel K. Inouye Solar Telescope (DKIST) in Hawaii have revealed “magnetic waves” in the sun’s atmosphere. These findings, published in Nature Astronomy, could explain the extreme heat in the corona.
DKIST, the largest ground-based solar telescope, has advanced our understanding of how energy moves through the sun’s atmosphere. Richard Morton, a solar physicist at Northumbria University, explained that prior studies struggled to pinpoint how the sun’s energy gets transferred to the atmosphere and solar wind, which flows at over 1 million mph (1.6 million km/h).
In 1942, Swedish physicist Hannes Alfvén theorized that these magnetic waves were key. Until now, scientists had not directly observed them in the corona. Morton pointed out that limitations of earlier instruments made it tough to see these waves clearly, leading to many assumptions in solar weather models.
Now, thanks to DKIST’s impressive 4-meter mirror and improved sensitivity, researchers have been able to observe these waves for the first time. Using the telescope’s unique Cryogenic Near Infrared Spectropolarimeter, scientists tracked the movement of the corona and detected the signature of Alfvén waves.
These waves appear as a pattern of red and blue Doppler shifts, indicating that they twist and turn within the plasma of the corona. Notably, the research indicates that these waves are not a rare occurrence; they are likely common throughout the sun’s atmosphere.
Morton emphasized that these waves could carry a significant amount of energy—potentially enough to account for half of what is needed to heat the corona. This finding complicates the current understanding of solar dynamics, which has mostly leaned towards magnetic reconnection—when twisted magnetic fields release energy—as the main heating mechanism.
The debate about whether solar waves or magnetic reconnection is the primary driver of coronal heating continues. However, both NASA’s Parker Solar Probe and the European Space Agency’s Solar Orbiter, along with DKIST’s new data, reinforce that both processes frequently occur in the sun’s atmosphere.
Understanding this balance of energy sources is crucial, not just for solar phenomena but also for understanding how other stars shine. The insight gained here could help scientists better predict solar winds and the behavior of planetary systems, offering a clearer view of their long-term evolution.
As ongoing research builds on these discoveries, it could shed light on the properties of Alfvén waves, enriching our models of solar behavior and enhancing our grasp of cosmic processes.
