研究者は高エネルギーレーザーを使用して磁気リコネクションを研究しています

科学者は、強力なレーザーを使用して小型の太陽フレアを作成し、磁気リコネクションのプロセスを研究しています。

科学者たちは、基本的な天文学的現象である磁気リコネクションの根底にあるメカニズムを調査するために、12個の高エネルギーレーザービームを使用して小さな太陽フレアをシミュレートしました。

一般に信じられていることとは反対に、宇宙は空ではありません。 「広大な宇宙」とは言え、宇宙には荷電粒子やガス、宇宙線など、さまざまな物質があふれています。 天体は珍しいように見えるかもしれませんが、宇宙は活発に活動しています。

空間を通過する粒子とエネルギーのそのようなドライブの 1 つは、磁気リコネクションと呼ばれる現象です。 名前が示すように、磁気リコネクションは、2 つの平行な磁場 (反対方向に移動する 2 つの磁場のように) が衝突し、壊れ、再整列するときに発生します。 無害に見えますが、穏やかとはほど遠いです。

この現象は宇宙のいたるところで見られます。 家では、太陽フレアや地球の磁気圏で見ることができます。 森田太一助教 九州大学 工学部および研究の最初の著者。 「実際、オーロラは、荷電粒子が地球磁場の磁気リコネクションから放出された結果として形成されます。」

しかし、それらは一般的に発生するものの、これらの現象の根底にあるメカニズムの多くは謎です. などの研究が行われている.[{” attribute=””>NASA’s Magnetospheric Multiscale Mission, where magnetic reconnections are studied in real-time by satellites sent into Earth’s magnetosphere. However, things such as the speed of reconnection or how energy from the magnetic field is converted and distributed to the particles in the plasma remain unexplained.

An alternative to sending satellites into space is to use lasers and artificially generate plasma arcs that produce magnetic reconnections. However, without suitable laser strength, the generated plasma is too small and unstable to study the phenomena accurately.

“One facility that has the required power is Osaka University’s Institute for Laser Engineering and their Gekko XII laser. It’s a massive 12-beam, high-powered laser that can generate plasma stable enough for us to study,” explains Morita. “Studying astrophysical phenomena using high-energy lasers is called ‘laser astrophysics experiments,’ and it has been a developing methodology in recent years.”

In their experiments, reported in Physical Review E, the high-power lasers were used to generate two plasma fields with anti-parallel magnetic fields. The team then focused a low-energy laser into the center of the plasma where the magnetic fields would meet and where magnetic reconnection would theoretically occur.

“We are essentially recreating the dynamics and conditions of a solar flare. Nonetheless, by analyzing how the light from that low-energy laser scatters, we can measure all sorts of parameters from plasma temperature, velocity, ion valence, current, and plasma flow velocity,” continues Morita.

One of their key findings was recording the appearance and disappearance of electrical currents where the magnetic fields met, indicating magnetic reconnection. Additionally, they were able to collect data on the acceleration and heating of the plasma.

The team plans on continuing their analysis and hopes that these types of ‘laser astrophysics experiments’ will be more readily used as an alternative or complementary way to investigate astrophysical phenomena.

“This method can be used to study all sorts of things like astrophysical shockwaves, cosmic-ray acceleration, and magnetic turbulence. Many of these phenomena can damage and disrupt electrical devices and the human body,” concludes Morita. “So, if we ever want to be a spacefaring race, we must work to understand these common cosmic events.”

Reference: “Detection of current-sheet and bipolar ion flows in a self-generated antiparallel magnetic field of laser-produced plasmas for magnetic reconnection research” by T. Morita, T. Kojima, S. Matsuo, S. Matsukiyo, S. Isayama, R. Yamazaki, S. J. Tanaka, K. Aihara, Y. Sato, J. Shiota, Y. Pan, K. Tomita, T. Takezaki, Y. Kuramitsu, K. Sakai, S. Egashira, H. Ishihara, O. Kuramoto, Y. Matsumoto, K. Maeda and Y. Sakawa, 10 November 2022, Physical Review E.
DOI: 10.1103/PhysRevE.106.055207

The study was funded by the Japan Society for the Promotion of Science.