Scientists uncover the mystery of fast magnetic explosions
Image credit: Siarhei Yurchanka | Dreamstime.com
A new theory about the causes of fast magnetic reconnection could forever change nuclear fusion research.
In just minutes, a flare on the Sun can release enough energy to power the whole world for 20,000 years. An explosive process called magnetic reconnection triggers these solar flares. However, scientists have struggled for over 60 years to understand how this happens.
Now, a research team within Nasa’s Magnetospheric Multiscale Mission (MMS) think they’ve figured it out.
The MMS team has developed a theory that explains how the most explosive type of magnetic reconnection – called fast reconnection – occurs. The new theory uses a common magnetic effect present in household devices, such as sensors that time vehicle anti-lock braking systems and know when a cell phone flip cover is closed.
“We finally understand what makes this type of magnetic reconnection so fast,” said lead researcher, Yi-Hsin Liu. “We now have a theory to explain it fully.”
If accurate, this theory could enable insights into nuclear fusion and provide better predictions of particle storms from the Sun that can affect Earth-orbiting technology.
Magnetic reconnection is a process that occurs in plasma, which originates when a gas has been energised enough to break apart its atoms, leaving a motley of negatively charged electrons and positively charged ions existing side-by-side. This energetic, fluid-like material is exquisitely sensitive to magnetic fields.
From flares on the Sun, to near-Earth space, to black holes, plasmas throughout the universe undergo magnetic reconnection, which rapidly converts magnetic energy into heat and acceleration. The most unknown type of magnetic reconnection is, undoubtedly, fast reconnection.
“We have known for a while that fast reconnection happens at a certain rate that seems to be pretty constant,” said Barbara Giles, project scientist for MMS. “But what really drives that rate has been a mystery, until now.”
The new research, published in a paper in Nature’s Communications Physics journal, and funded in part by the National Science Foundation, explains how fast reconnection occurs in collisionless plasmas – a type of plasma whose particles don’t collide with one another. Most of the plasma present in space, including that of solar flares and the space around Earth, is of this variant.
The new theory shows how and why fast reconnection is likely sped up by the Hall effect, which describes the interaction between magnetic fields and electric currents.
During fast magnetic reconnection, charged particles in a plasma stop moving as a group. As the ions and electrons begin moving separately, they create an unstable energy vacuum where reconnection happens. Pressure from the magnetic fields around the energy vacuum causes the vacuum to implode, releasing immense amounts of energy at a predictable rate.
Fusion research has been growing significantly in recent months, with the UK Atomic Energy Authority initiating a consultation in January 2021 to ask residents in five areas to provide feedback on potential plans to construct a prototype nuclear fusion power plant. Moreover, the government published its own white paper outlining plans for regulating the rollout of fusion energy.
The new theory will be tested in the coming years with MMS, which uses four spacecraft flown around Earth in a pyramid formation to study magnetic reconnection in collisionless plasmas. In this unique space laboratory, MMS can study magnetic reconnection at a higher resolution than it would be possible to do on Earth.
“Ultimately, if we can understand how magnetic reconnection operates, then we can better predict events that can impact us at Earth, like geomagnetic storms and solar flares,” Giles said.
“If we can understand how reconnection is initiated, it will also help energy research because researchers could better control magnetic fields in fusion devices.”
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