Solar waves in UK-size magnetic hole

U. SHEFFIELD (UK) — Massive waves in giant magnetic holes on the surface of the Sun have been discovered for the first time.

The Sun is interwoven by a complex network of magnetic field lines. Large, dark regions, which look like holes on the Sun’s surface, mark out areas where the magnetic field breaks through from the Sun’s deep, boiling interior and rises into the very hot solar atmosphere, which is over a million degrees. The largest of these dark regions are often called sunspots and have been studied since their discovery from as early as 364 BC.

Solar scientists were studying a magnetic region of the Sun much smaller than a sunspot—still many times greater than the size of the U.K. The magnetic hole they observed, which is also known as a pore, is able to channel energy generated deep inside the Sun, along the magnetic field to the upper atmosphere.

The magnetic field emerging through the pore is over 1,000 times stronger than the magnetic field of the Earth.

The energy being transported is in the form of a very special form of waves, known as “sausage waves,” which the scientists were able to observe using a solar imager known as ROSA (Rapid Oscillations of the Solar Atmosphere). The imager, designed by Queen’s University Belfast, is in operation at the Dunn Solar Telescope in New Mexico.

This is the first direct observation of sausage waves at the solar surface. The magnetic hole is seen to increase and decrease in size periodically which is a characteristic feature of the sausage wave. Findings are reported in the Astrophysical Journal.

Researchers hope these giant magnetic holes will play an important role in unveiling the longstanding secrets behind solar coronal heating.

“This is a fascinating new discovery in line with a number of discoveries made in recent years by the team. It is the first time that ‘sausage waves’ have been detected in the Sun with such detail. Analyzing these waves may bring us closer to understanding the physical mechanisms in the atmosphere of a star,” says Robertus von Fay-Siebenburgen, director of the Solar Physics and Space Plasma Research Centre at the University of Sheffield.

Sun’s secrets
The solar surface has a temperature of a few thousand degrees but the solar corona—the outermost, mysterious, and least understood layer of the Sun’s atmosphere—is heated to temperatures often a thousand times hotter than the surface.

Why the temperature of the Sun’s atmosphere increases as we move further away from the center of energy production, which lies under the surface, is a great mystery of astrophysics. The findings, which demonstrate the transfer of energy on a massive scale, offer a new explanation for this puzzle.

The team now hope to use further similar solar images from ROSA to understand the fine substructure of these massive magnetic holes by reconstructing the images to view what is inside the holes.

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