SDO reveals how magnetic cage on the Sun stopped solar eruption

February 23, 2018 by Lina Tran, NASA's Goddard Space Flight Center
On Oct. 24, 2014, NASA's SDO observed an X-class solar flare erupt from a Jupiter-sized sunspot group. Credit: Tahar Amari et al./Center for Theoretical Physics/École Polytechnique/NASA Goddard/Joy Ng

A dramatic magnetic power struggle at the Sun's surface lies at the heart of solar eruptions, new research using NASA data shows. The work highlights the role of the Sun's magnetic landscape, or topology, in the development of solar eruptions that can trigger space weather events around Earth.

The scientists, led by Tahar Amari, an astrophysicist at the Center for Theoretical Physics at the École Polytechnique in Palaiseau Cedex, France, considered solar flares, which are intense bursts of radiation and light. Many strong solar flares are followed by a , or CME, a massive, bubble-shaped eruption of solar material and magnetic , but some are not—what differentiates the two situations is not clearly understood.

Using data from NASA's Solar Dynamics Observatory, or SDO, the scientists examined an October 2014 Jupiter-sized sunspot group, an area of complex magnetic fields, often the site of solar activity. This was the biggest group in the past two solar cycles and a highly active region. Though conditions seemed ripe for an eruption, the region never produced a major CME on its journey across the Sun. It did, however, emit a powerful X-class flare, the most intense class of flares. What determines, the scientists wondered, whether a flare is associated with a CME?

The team of scientists included SDO's observations of magnetic fields at the Sun's surface in powerful models that calculate the of the Sun's corona, or upper atmosphere, and examined how it evolved in the time just before the flare. The model reveals a battle between two key magnetic structures: a twisted magnetic rope—known to be associated with the onset of CMEs—and a dense cage of magnetic fields overlying the rope.

In this series of images, the magnetic rope, in blue, grows increasingly twisted and unstable. But it never erupts from the Sun's surface: The model demonstrates the rope didn't have enough energy to break through the magnetic cage, in yellow. Credit: Tahar Amari et al./Center for Theoretical Physics/École Polytechnique/NASA Goddard/Joy Ng

The scientists found that this magnetic cage physically prevented a CME from erupting that day. Just hours before the flare, the sunspot's natural rotation contorted the magnetic rope and it grew increasingly twisted and unstable, like a tightly coiled rubber band. But the rope never erupted from the surface: Their model demonstrates it didn't have enough energy to break through the cage. It was, however, volatile enough that it lashed through part of the cage, triggering the strong solar flare.

By changing the conditions of the cage in their model, the scientists found that if the cage were weaker that day, a major CME would have erupted on Oct. 24, 2014. The group is interested in further developing their model to study how the conflict between the magnetic cage and rope plays out in other eruptions. Their findings are summarized in a paper published in Nature on Feb. 8, 2018.

"We were able to follow the evolution of an active region, predict how likely it was to erupt, and calculate the maximum amount of energy the can release," Amari said. "This is a practical method that could become important in space weather forecasting as computational capabilities increase."

Explore further: Toward a better prediction of solar eruptions

More information: Tahar Amari et al. Magnetic cage and rope as the key for solar eruptions, Nature (2018). DOI: 10.1038/nature24671

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katesisco
1 / 5 (1) Feb 24, 2018
Well, if V Zharkova is correct and there is a SECOND MAGNETIC FIELD OF THE SUN UNDERLYING THE SURFACE, then during solar minimum, it is possible the secondary underlying field will produce strong eruptions that break thru and blast Earth as the Carrington Event did.
cantdrive85
3 / 5 (4) Feb 24, 2018
The plasma ignoramuses only study the magnetism in electromagnetism and wonder why they can't resolve reality and why there are continued mysteries. One must account for the energy source, transport, and dissipation. In other words, don't forget the electric currents.
https://www.ann-g...65/2017/
cantdrive85
2 / 5 (3) Feb 24, 2018
The above paper seems to agree with Akasofu's paper I linked. From the abstract;
"Two types of model have been developed to identify the mechanism that triggers confined flares, although it has hitherto not been possible to decide between them because the magnetic field at the origin of the flares could not be determined with the required accuracy3,4,5,6,7,8.**(just as Akasofu mentioned)** In the first type of model, the triggering is related to the topological complexity of the flaring structure, which implies the presence of magnetically singular surfaces9,10,11. **(this is MRx)** This picture is observationally supported by the fact that radiative emission occurs near these features in many flaring regions12,13,14,15,16,17. The second type of model attributes a key role to the formation of a twisted flux rope, which becomes unstable."
A "twisted flux rope" is of course a Birkeland current. This is the electric current model Akasofu's paper is about. All they need is the "dynamo".

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