The Sun is literally wrapped in a mystery. The solar corona, the aura of plasma that surrounds our star, has a temperature in the millions of degrees, hundreds of times hotter than the surface of the Sun, the so-called photosphere. Many scientists are trying to solve the enigma of this temperature difference.
In a new paper published in Nature Communications, researchers have observed the presence of magnetic plasma pulses known as Alfvén pulses within the chromosphere, the thin layer between the solar surface and the corona that's visible as a red ring during solar eclipses. The team observed that at any given time, there are at least 150,000 swirls of plasma from the photosphere, each as large as Oregon (or the British Isles).
“Swirling motions are everywhere in the universe, from sinking water in domestic taps with a size of centimeters, to tornadoes on Earth and on the Sun, solar jets and spiral galaxies with a size of up to 520,000 light-years. This work has shown, for the first time, the observational evidence that ubiquitous swirls in the solar atmosphere could generate short-lived Alfvén pulses,” co-author Professor Robertus Erdélyi, from the University of Sheffield, said in a statement.
The Alfvén pulses are particular motions of particles in the plasma. They can go through the solar atmosphere along the cylindrical magnetic tubes that form in the region. In this way, they can reach the higher layer of the chromosphere and maybe even beyond in the corona, bringing a lot of energy with them.
“The energy flux carried by the Alfvén pulses we detected now are estimated to be more than 10 times higher than that needed for heating the local upper solar chromosphere,” lead author Dr Jiajia Liu, explained.
“We believe, these UK-sized photospheric magnetic plasma swirls are also very promising candidates not just for energy but also for mass transportation between the lower and upper layers of the solar atmosphere,” Erdélyi added.
The team will continue to investigate these swirls to understand if and how much they contribute to coronal heating. More detailed data about the solar corona will come from the Parker Solar Probe, which is currently on an orbit that will take it closer and closer to our star over the next few years.