Scientists Finally Solve 70-Year Mystery of Sun’s ‘Impossible Heat
Scientists Detect Elusive waves, Cracking 70-Year Mystery of the Sun’s Scorching Corona
LONDON – after decades of examination, scientists have directly observed torsional Alfvén waves within the Sun’s corona, a breakthrough that helps explain the long-standing mystery of why the Sun’s outer atmosphere is millions of degrees hotter than its surface. The findings, published in Nature Astronomy, confirm a key component of theories explaining the Sun’s energy transfer and could improve predictions of disruptive space weather events.
For 70 years, astronomers have puzzled over the ”coronal heating problem” – the fact that the corona, the Sun’s outermost layer, reaches temperatures exceeding 1 million degrees Celsius, while the visible surface is only around 5,500 degrees Celsius. Various theories have been proposed, centering on the role of magnetic waves traveling through the Sun’s plasma. Alfvén waves, in particular, were suspected as a major contributor, but directly detecting the twisting, torsional component of these waves proved incredibly difficult.
Researchers, led by Dr. Eric Morton of Northumbria University,utilized data from the Swedish 1-meter Solar Telescope to isolate these subtle motions. “The movement of plasma in the Sun’s corona is dominated by swaying motions,” Morton explains. “These mask the torsional motions, so I had to develop a way of removing the swaying to find the twisting.” By filtering out the more prominent swaying motions, the team was able to reveal the presence of the small-scale torsional Alfvén waves.
These waves are believed to play a crucial role in both heating the corona to its extreme temperatures and driving the solar winds that stream outwards from the Sun, potentially impacting earth. The solar winds, capable of disrupting satellite networks and power grids, are now better understood thanks to this discovery.
“Small-scale torsional Alfvén waves might potentially be contributing to the forces needed to push these winds beyond the influence of the Sun’s gravity,” the study notes. Improved understanding of these processes will allow for more accurate space weather forecasts and warnings of potentially damaging geomagnetic storms.
Morton emphasizes the importance of this observational validation: “This research provides essential validation for the range of theoretical models that describe how Alfvén wave turbulence powers the solar atmosphere. Having direct observations finally allows us to test these models against reality.” Future research will focus on mapping the distribution and mechanisms of these waves across the corona, and further refining our understanding of the Sun’s complex dynamics.