2026-10-13 東京大学
太陽探査機「パーカー・ソーラー・プローブ」
Image credit: NASA/Johns Hopkins APL/Steve Gribben
＜関連情報＞
- https://www.s.u-tokyo.ac.jp/ja/press/11251/#
- https://iopscience.iop.org/article/10.3847/2041-8213/aea84b
磁気流体力学-運動学的界面における磁気ヘリシティの非局所的進化 Nonlocal Evolution of Magnetic Helicity across the Magnetohydrodynamic–Kinetic Interface
Masatomi Iizawa, Yasuhito Narita, Tommaso Alberti, Stuart D. Bale, Axel Brandenburg, Abraham C.-L. Chian, Horia Comişel, Shuichi Matsukiyo, and Nobumitsu Yokoi
The Astrophysical Journal Letters Published: 2026 October 13
DOI:10.3847/2041-8213/aea84b
Abstract
Magnetic helicity is typically indistinguishable from noise in the solar wind inertial range. Using Parker Solar Probe measurements (0.1–0.8 au), we report a robust bihelical structure emerging at the magnetohydrodynamic (MHD)–kinetic interface. This structure, formed by a striking pair of positive and negative peaks, exhibits a systematic spectral migration toward lower frequencies with increasing heliocentric distance. Crucially, this evolution deviates from local kinetic scaling laws, such as the radial decline of the ion cyclotron frequency, reflecting a nonlocal evolution of magnetic topology. Our findings provide a new observational constraint on both nonlocal MHD transport processes and the nature of the helicity barrier in the kinetic regime.
