2023-06-01 フィンランド・アールト大学
◆さらに、小規模ダイナモは超伝導コンピュータなどの応用にも役立つ可能性があります。今後は小規模ダイナモと大規模ダイナモの相互作用や太陽周期についての研究が展開される予定です。
＜関連情報＞
- https://www.aalto.fi/en/news/supercomputer-simulations-provide-a-better-picture-of-the-suns-magnetic-field
- https://www.nature.com/articles/s41550-023-01975-1
太陽磁気のプランドル数に近づく小規模なダイナモの数値的証拠 Numerical evidence for a small-scale dynamo approaching solar magnetic Prandtl numbers
Jörn Warnecke,Maarit J. Korpi-Lagg,Frederick A. Gent & Matthias Rheinhardt
Nature Astronomy Published:18 May 2023
DOI:https://doi.org/10.1038/s41550-023-01975-1
Abstract
Magnetic fields on small scales are ubiquitous in the Universe. Although they can often be observed in detail, their generation mechanisms are not fully understood. One possibility is the so-called small-scale dynamo (SSD). Prevailing numerical evidence, however, appears to indicate that an SSD is unlikely to exist at very low magnetic Prandtl numbers (PrM) such as those that are present in the Sun and other cool stars. Here we have performed high-resolution simulations of isothermal forced turbulence using the lowest PrM values achieved so far. Contrary to earlier findings, the SSD not only turns out to be possible for PrM down to 0.0031 but also becomes increasingly easier to excite for PrM below about 0.05. We relate this behaviour to the known hydrodynamic phenomenon referred to as the bottleneck effect. Extrapolating our results to solar values of PrM indicates that an SSD would be possible under such conditions.
