Alfvén Waves Discovered on the Sun

Solar physicists proposed the existence of powerful magnetic plasma waves called Alfvén waves many years ago, but thus far evidence to prove they actually form have been scarce at best. A new study now identifies the formations with a great deal of accuracy.

The work represents the first time that the powerful waves are found in the Sun’s corona, experts say. They add that the superheated gas called plasma inside these structures was observed to move at speeds exceeding 200 to 250 kilometers per second.

Researches conducted by Katholieke Universiteit Leuven (K.U.Leuven) Center for Plasma Astrophysics professor Marcel Goossens used the NASA Solar Dynamics Observatory (SDO) to conduct the new investigation.

The speed at which these waves were found to travel could cover the distance between Leuven in Flanders, Belgium and New York in roughly 30 seconds. The reason why this is important is that understanding these waves may clear a number of mysteries still surrounding the solar corona.

For example, physicists don't yet have good grasp of why the corona is way hotter than the actual surface of the Sun. At the same time, their models cannot really account for the very high speed of solar winds, Space reports.

The Alfvén waves may be compared to transversal waves on taut wires, Goossens explains. “One might conceive of the magnetic field lines as taut wires loaded with mass (plasma),” he goes on to say.

“If the wire is pulled off balance and then released, creating a catapult effect, the wire will move backwards and forwards as a result of the power of tension,” the expert explains.

“This sideways (transversal) movement runs along the wire as a wave. These transversal waves are called Alfvén waves when they occur on magnetic field lines loaded with plasma,” he adds.

The waves are named after Swedish scientist Hannes Alfvén, who first proposed their existence back in 1942. No type of evidence – or the technologies to get them – were available at the time, so all the work had to be done theoretically.

Though the international scientific community was reluctant to accept the discovery at first, it later came around, and recognized the high significance of the work Alfvén carried out. The expert won a Nobel Prize for Physics in 1970, in recognition of his studies.

Details of the new discoveries in the solar corona appear in the latest issue of the top scientific journal Nature. The work's main conclusion is that Alfvén waves move sufficiently fast to heat the corona, and accelerate solar winds to their observed speeds.