High-Power Laser Creates a Miniature Magnetosphere

Pure electron outflows linked with magnetic reconnection generated by electron dynamics in plasmas created by lasers are first experimentally measured.

The tiny electron dynamics, which are important to space and astrophysical events, have been better understood by looking at magnetic reconnections in laser-produced plasmas. Using a high-power laser called Gekko XII at the Institute of Laser Engineering, Osaka University scientists have reported the direct measurements of pure electron outflows pertinent to magnetic reconnection. They were conducted in collaboration with researchers at the National Institute for Fusion Science and other universities. Today, June 30, 2022, Springer Nature, Scientific Reports will publish their results.

Many space and astrophysical events, including solar flares and magnetic substorms, where the magnetic energy is released as plasma energy, depend on the fundamental mechanism of magnetic reconnection. It is well known that electron dynamics are crucial to the magnetic reconnection's triggering process. It has, however, proven to be quite difficult to monitor the minute electron-scale processes in the enormous cosmos.

(a) Schematics of the experiment. By irradiating a plastic target with the Gekko XII laser, plasma flow is generated in the presence of a weak magnetic field. The weak magnetic field is distorted by the dynamic pressure of the plasma flow and the anti-parallel magnetic configuration is created. (b) The insert schematically shows that the elongated magnetic field reconnects and releases the magnetic field energy as the reconnection outflows. Pure electron outflows have been measured with CTS for the first time in laser-produced plasmas. Credit: 2022 K. Sakai et al. Direct observations of pure electron outflow in magnetic reconnection. Scientific Reports

As a result, in plasmas generated by lasers, scientists formed situation-only electrons that were directly associated with a magnetic field. The 'laboratory astrophysics' gives researchers access to the tiny universe.

“In space plasmas, the key players sometimes hide in the small scale. It is very difficult to see their actions in large-scale space phenomena, even via cutting-edge numerical simulations,” says Toseo Moritaka, the author of the study. “Now laser experiments can arrange a new stage to shed light on their actions. The results will bridge various observations and simulations in macroscopic and microscopic points of view.”

The pure electron outflow connected to the electron-scale magnetic reconnection in laser-produced plasmas has been detected for the first time using collective Thomson scattering measurements.

“The outcomes of this research are applicable not only to space and astrophysical plasmas, but also to magnetic propulsion of spacecrafts and also fusion plasmas,” says Yasuhiro Kuramitsu, the principal author of the research. “Microscopic electron dynamics governs macroscopic phenomena, such as magnetic reconnections and collisionless shocks. This is a unique and universal property of plasma, which is not seen in ordinary gas and liquid.

“Now we can address this in laboratories by direct local measurements of the plasma and magnetic field. We will tackle long-standing open problems in the universe by modeling them in laboratories. Knowing the nature of plasmas may lead us to realize, for example, fusion plasma.”

Reference: “Direct observations of pure electron outflow in magnetic reconnection” 30 June 2022, Scientific Reports.
Funding: Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology-Japan