NASA scientists have modeled a theory to explain how the Sun’s most powerful type of magnetic reconnection takes place. Why does it happen at such a constant rate?
Discovered one of the many secrets of the Sun
There is a type of solar flare that lasts a few minutes but produces enough energy to power the Earth for 20,000 years at a fast and predictable rate. For more than half a century, scientists have been trying to understand the process, called fast magnetic reconnection, and it seems that they have already found the result, according to a report from the US space agency.
“Ultimately, if we can understand how magnetic reconnection works, then we can better predict events that may impact us on Earth, such as geomagnetic storms and solar flares ,” explained Barbara Giles, project scientist for MMS and research scientist at the Center. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, USA.
The study, published in the journal Communications Physics, provides the first theoretical description of how a phenomenon known as the “Hall effect” – the interaction between electric currents and the magnetic fields that surround them – determines the efficiency of magnetic reconnection.
What exactly is magnetic reconnection?
This phenomenon occurs when magnetic field lines from opposite directions merge, rejoin, and separate, releasing massive amounts of energy to heat plasmas and drive high-velocity outflows.
“The rate at which magnetic field lines reconnect is of extreme importance to processes in space that can impact Earth,” said Yi-Hsin Liu, an assistant professor of physics and astronomy at Dartmouth. “After decades of effort, we now have a complete theory to address this long-standing problem.”
The precise physics behind this release of energy
Magnetic reconnection is a multifaceted energy conversion process that occurs in plasma. It forms when the gas has been energized enough to break apart its atoms, leaving behind negatively charged electrons and positively charged ions. In this process, the plasma rapidly converts magnetic energy into heat and acceleration.
“We knew that fast reconnection occurs at a certain rate that appears to be fairly constant. But what drives that rate has been a mystery until now,” says Giles. In the new work, they explain how quickly reconnection occurs, specifically in collisionless plasmas (those whose particles are spread out enough that individual particles don’t collide with each other). Where reconnection occurs in space, most of the plasma is in this collisionless state, including plasma in solar flares and the space around Earth.
According to the new theory, charged particles in the plasma stop moving as a group during rapid magnetic reconnection. They begin to move independently, giving rise to the Hall effect and thus creating an unstable energy vacuum where the reconnection occurs. The pressure of the magnetic fields around the energy void causes the void to implode, rapidly releasing immense amounts of energy at a predictable rate.
So, this new research proposes that fast reconnection takes place only in collisionless plasmas.
How to check the theory?
Scientists at NASA’s Multiscale Magnetospheric Mission (MMS) will test their theory with the help of four spacecraft orbiting the Earth in a pyramid formation , allowing them to investigate the reconnection process in collisionless plasmas at higher resolutions than previously known. would be possible on Earth.
Will we thereby unlock the potential of nuclear fusion and, by extension, achieve unlimited sustainable energy for everyone on our planet?
Referencia: “First-principles theory of the rate of magnetic reconnection in magnetospheric and solar plasmas” by Yi-Hsin Liu, Paul Cassak, Xiaocan Li, Michael Hesse, Shan-Chang Lin and Kevin Genestreti, 28 April 2022, Communications Physics.
DOI: 10.1038/s42005-022-00854-x
This work is funded by the NSF’s PHY and AGS Divisions, NASA’s Magnetospheric Multiscale (MMS) mission, and the U.S. Department of Energy.
