As we all know, the Sun is a giant ball of plasma, and like any plasma, it should support Alfven waves. Alfven waves are waves in a plasma where the ions move in response to tension from a magnetic field. Scientists predicted it 50 years ago until now we had not been able to see them. But recently, astronomers have found them while observing the Sun’s photosphere (the lowest layer of the Sun’s atmosphere and the region that releases the light that we can see). This discovery may help explain why the solar corona is so much hotter than the surface.
Despite previous claims, Alfven waves had never conclusively been found on the Sun before. A team of researchers, led by Dr Marco Stangalini at Italian Space Agency (ASI, Italy) with scientists from seven other research institutes and universities, including Queen Mary’s Dr David Tsiklauri and PhD student Callum Boocock, used the European Space Agency’s IBIS to monitor the Sun’s photosphere carefully. This careful observation of the Sun’s photosphere led them to observe the Alfven waves for the first time.
Magnetic fields in the Sun can bundle together, forming long structures called flux tubes. These flux tubes can drive the formation of Alfven waves. The researchers validated their observations with the aid of magnetohydrodynamic (MHD) simulations, which are computer simulations of the complex plasma physics operating at the Sun’s surface.
Callum Boocock, a PhD student at Queen Mary’s School of Physics and Astronomy, said: “The observations of torsional Alfven waves made by Marco and his team were remarkably similar to the behaviour seen in our MHD simulations, demonstrating the importance of these simulations for discovering and explaining wave generation mechanisms.”
The finding provides a crucial step to understanding why the outer solar atmosphere, the corona, has a temperature a million degrees hotter than the surface. Something much be transporting energy from the photosphere to the corona, and these Alfven waves may be the culprit.