近日，美国哥伦比亚大学B. Tripathi团队研究了由剪切流诱导射流驱动的大型发电机。相关论文于2026年1月21日发表在《自然》杂志上。

在它们占据的每一个尺度上，磁场都影响着多种现象，包括恒星形成、宇宙射线传输、带电粒子加速、空间天气、行星大气与实验室等离子体中的传输过程。这些磁场通常由湍流在一种称为"发电机"的过程中产生和维持。1955年，E. N. 帕克通过参数化小尺度湍流效应，提出了平均场发电机理论。这一被广泛使用的理论成功复现了观测到的大尺度磁场，但其参数调校存在困难，因为它们并非基于第一性原理：湍流研究显示磁场呈现纠缠状态，在剪切流应变作用下被折叠并碎裂为小尺度结构。

研究组通过考虑一个不稳定且受驱动的剪切流，发展了解析理论并执行了最高达4096×4096×8192网格点的三维先进湍流数值模拟，首次展示了准周期性大尺度磁场的从头生成机制。该生成过程通过平均涡度效应实现——这是1990年被提出的另一种平均场发电机过程。此发电机的关键在于事先生成的大尺度三维喷流，它们作为磁流体动力学方程组的拓扑保护精确非线性解被稳定产生。喷流驱动的发电机机制适用于剪切驱动的实验室系统与天体物理系统，包括双中子星并合事件——该过程中报告的发电机机制可能在微秒时间尺度上运行，并在毫秒级时间内产生宇宙中最强的磁场之一，从而为多信使天文学提供探测信号。

附：英文原文

Title: Large-scale dynamos driven by shear-flow-induced jets

Author: Tripathi, B., Fraser, A. E., Terry, P. W., Zweibel, E. G., Pueschel, M. J., Fan, R.

Issue&Volume: 2026-01-21

Abstract: At every scale they occupy, magnetic fields affect various phenomena, including star formation, cosmic-ray transport, charged-particle acceleration, space weather, transport in planetary atmospheres and laboratory plasmas. These fields are often generated and sustained by turbulent flows in a process called the dynamo. In 1955, E. N. Parker parameterized the effects of small-scale turbulence to propose a mean-field dynamo theory1. The widely used theory reproduces observed large-scale fields but suffers from difficulty in tuning parameters as they are not justified from first principles: studies of turbulent flows show tangled magnetic fields, which are folded and fragmented into small-scale structures owing to shear-flow straining2,3. Here, considering a shear flow that is unstable and driven, we develop analytic theory and perform three-dimensional, advanced computer simulations of turbulence with up to 4,096×4,096×8,192 grid points, showing ab initio generation of quasi-periodic, large-scale magnetic fields. The generation occurs via the mean-vorticity effect—an additional mean-field dynamo process postulated4 in 1990. Crucial to this dynamo is the prior generation of large-scale three-dimensional jets, robustly produced as topologically protected and exact nonlinear solutions of the magnetohydrodynamic equations. The jet-driven dynamo applies to shear-driven laboratory and astrophysical systems. These include binary neutron star mergers5,6, where the reported dynamo probably operates on microsecond timescales to produce in milliseconds some of the strongest magnetic fields in the Universe7, providing signals for multi-messenger astronomy8.

DOI: 10.1038/s41586-025-09912-0

Source: https://www.nature.com/articles/s41586-025-09912-0