U. SHEFFIELD (UK)—Solar physicists have recorded the musical sounds created by longitudinal vibrations within the Sun’s atmosphere—and revealed that the sounds are caused by the movement of giant magnetic loops in the solar corona.

The team is investigating how this sound is decaying, giving an unprecedented insight into the physics of the  corona—the outermost, mysterious, and least understood layer of the Sun’s atmosphere.

High-resolution images taken by a number of satellites show that the solar corona is filled with large banana-shaped magnetic structures known as coronal loops.

It is thought that these giant magnetic loops, some of them over a few 100,000 km long, play a fundamental role in governing the physics of the corona and are responsible for huge atmospheric explosions that occur in the atmosphere, known as solar flares.

These giant coronal loops have also been observed to undergo periodic (oscillatory) motion, which can be thought of as someone plucking a guitar string (transversal oscillations) or blowing the wind-pipe instrument (longitudinal oscillations).

With the length and thickness of the string fixed, the pitch of the note is determined by the tension of the string and the tone is made up of the harmonics of the modes of oscillation.

In this sense, the solar atmosphere is constantly pervaded by the music of the coronal loops. The coronal music also provides scientists with a unique and unprecedented tool to study the magnetic solar atmosphere, as the motion of these loops is determined by their local surroundings.

This technique is known as solar magneto-seismology and is very similar to the seismology methods used by geologists studying earthquakes.

Studying this magnetic solar atmosphere will help the team, which is led by University of Sheffield professor Robertus von Fáy-Siebenbürgen, make further breakthroughs into understanding one of the key and central unresolved problems of modern astrophysics: the heating of solar and tellar coronal plasmas.

The work may also help clarify the underlying physical processes: Are there millions of localized magnetic explosions releasing the energy necessary to maintain the corona at millions of degrees, or is the physics related to the numerous waves propagating from the internal regions of the Sun toward its outer regions, reaching even space around the Earth’s atmosphere?

The next step for the team will be to develop numerical modeling that will be able to give further insight into the sub-resolution properties of coronal loops—on spatial scales that are not even observable with the latest high-resolution satellites available to scientist.

According to von Fáy-Siebenbürgen, the latest findings “allow us to gain a fundamentally new insight into the fascinating but at the same time very mysterious solar atmosphere.”

Audio of a ‘kink’: a transverse oscillation similar to a guitar string being plucked. (Credit: Richard Morton)

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