Chinese researchers employ powerful lasers to recreate solar flares
On January 10, NASA's Solar Dynamics Observatory recorded a massive X-class solar flare. The blast hurled debris into space, and radiation from the flare triggered radio blackouts across the South Pacific. The solar outburst was the third X-class — the most powerful — flare in less than a week.
These intense bursts of radiation from the release of magnetic energy associated with sunspots can be dangerous - in February 2022, SpaceX lost 40 of its newly launched Starlink communications satellites due to a geomagnetic storm triggered by a solar flare.
To better understand solar flares and protect satellites, and power grids on Earth, for the first time, researchers in China have used powerful lasers to recreate magnetic explosions on the surface of the Sun, South China Morning Post reported.
The team stimulated a turbulent magnetic reconnection in which the Sun's anti-parallel magnetic fields dramatically collide, break, and realign. In the process, it unleashes a massive amount of radiation into space. These particles form solar flares that can reach the Earth.
"We reproduced the rather chaotic and complex reconnection process in the laboratory and demonstrated typical changes during solar flares which had been observed by telescope missions," Beijing Normal University astronomy professor Zhong Jiayong, the study’s lead author, told SCMP.
An simple version of the magnetic reconnection experiment conducted years ago
The results were published in the peer-reviewed international journal Nature Physics on Monday.
“Compared with telescope observation, laboratory simulation is often more controllable and time-saving. It allows scientists to build more reliable models and better predict when and where magnetic reconnection is going to happen,” Jiayong said. Over a decade ago, Zhong and his team from the Chinese Academy of Sciences, Peking University, and Shanghai Jiao Tong University conducted a toned-down version of the experiment.
"In that experiment, we properly scaled key parameters to make sure it is compatible with an actual solar flare on the sun," Zhong said.
In 2010, they recreated magnetic reconnection by employing two high-power lasers to trigger an aluminum foil and generate plasma bubbles. As these bubbles expanded, the magnetic fields collided, and magnetic reconnection was observed.
Zhong mentioned that the original phenomenon of the Sun was much more complex, while the experiment only mimicked a simple version of magnetic reconnection.
The facility can form a high-temperature plasma for various experiments
The new study saw a larger interaction area for the turbulence, along with double the number of lasers and amount of aluminum foil.
"Though turbulence is everywhere in our daily life, from a fast-flowing river to the smoke from a chimney, it remains a highly complicated subject. Turbulence research used to be confined to a small community and focused only on the theoretical aspects, and I’m glad to see experimental studies of turbulence are now taking off," Zhong said.
The recreated facility can "shoot laser beams with a power more than the total output of global power grids within one-billionth of a second and form a high-temperature plasma for various laser-plasma interaction experiments," SCMP reported.
The experiments were conducted at the ShenGuang II laser facility in Shanghai, which consists of an eight-beam laser system and a multifunctional high-energy laser system.
Turbulent magnetic reconnection is believed to occur in astrophysical plasmas, and it has been suggested to be a trigger of solar flares. It often occurs in long stretched and fragmented current sheets. Recent observations by the Parker Solar Probe, the Solar Dynamics Observatory and in situ satellite missions agree with signatures expected from turbulent reconnection. However, the underlying mechanisms, including how magnetic energy stored in the Sun’s magnetic field is dissipated, remain unclear. Here we demonstrate turbulent magnetic reconnection in laser-generated plasmas created when irradiating solid targets. Turbulence is generated by strongly driven magnetic reconnection, which fragments the current sheet, and we also observe the formation of multiple magnetic islands and flux-tubes. Our findings reproduce key features of solar flare observations. Supported by kinetic simulations, we reveal the mechanism underlying the electron acceleration in turbulent magnetic reconnection, which is dominated by the parallel electric field, whereas the betatron mechanism plays a cooling role and Fermi acceleration is negligible. As the conditions in our laboratory experiments are scalable to those of astrophysical plasmas, our results are applicable to the study of solar flares.