New research has made the first clear detection of small-scale torsional Alfvén waves in the solar corona and solved a long-standing mystery about our star’s temperatures.
Scientists have finally found direct evidence of a crucial phenomenon that could explain one of the Sun’s greatest mysteries: why its outer atmosphere, or corona, burns at millions of degrees while its surface remains relatively cold?
An international research team, led by physicist Richard Morton, has reported the first clear detection of small-scale torsional Alfvén waves in the solar corona. These waves twist and travel along the Sun’s magnetic field lines, transporting plasma and energy upward in a process that has long been suspected of playing a role. crucial role in warming the corona and in the generation of solar wind.
The discoveries, published in the journal Nature Astronomy, mark the culmination of a scientific quest that began in the 1940s. “This discovery ends a long search for these waves,” said Morton. “We are finally able to directly observe these torsional movements that distort the magnetic field lines in the corona.”
Previous research has only identified large Alfvén waves associated with solar flares, explosive events that release energy briefly. Smaller, more continuous versions of these waves had already been theorized, but never observed directly until now.
The discovery was made possible thanks to the Daniel K. Inouye Solar Telescope in Hawaii, the most powerful solar observatory in the world. Using their high-resolution instruments, scientists tracked the movement of superheated iron plasma in the solar corona, detecting subtle changes in color: bluer light as the material moved towards Earth and redder as it moved away. By filtering out the more dominant plasma oscillation motions, the researchers revealed the torsion Alfvén waves hidden beneath.
“The movement of plasma in the solar corona is dominated by oscillation movements,” explained Morton. “These movements mask twisting movementsso I had to develop a way to remove the wobble to find the twist.”
The discovery offers a clearer view of how the Sun’s energy travels through its atmosphere, helping to explain both the extreme heat of the corona and the acceleration of solar winds that course through the solar system. These winds can have profound effects on Earth, from satellite disruption up to the triggering of geomagnetic storms.
As Morton notes, “having direct observations allows us to finally test these models against reality”.
