近日，美国约翰斯·霍普金斯大学Savvas Raptis团队报道了木星弓形激波及更远处的相对论电子加速。该研究于2026年6月3日发表在《自然》杂志上。

无碰撞激波在宇宙空间等离子体中普遍存在，被广泛认为是宇宙射线加速的主要场所。主流的扩散激波加速机制要求粒子反复穿越激波波前，每次穿越都获得能量。粒子所能达到的最大能量从根本上受到希拉斯判据的约束，该判据将加速区域的物理尺度与粒子最大能量联系起来。然而，由于对加速区域直接观测约束的匮乏，学界难以预测大多数天体物理系统中粒子的最大能量。

研究组利用美国国家航空航天局（NASA）朱诺号探测器的数据，展示了在木星弓形激波上游，由大尺度前激波瞬变现象驱动的相对论电子（≥1?MeV）加速的直接证据。结合这些数据及互补的太阳系观测结果，研究组提出了一个希拉斯极限的普适标度律，从经验上将可观测的瞬变现象尺度与粒子最大能量联系起来。将该标度律应用于从行星弓形激波?到原恒星喷流?以及超新星遗迹?等不同环境，得到了一个从兆电子伏尺度到约几十吉电子伏、再到约几十太电子伏的粒子最大可获得能量的简单模型，为在天体物理激波处约束宇宙射线的最大能量提供了基于观测的方法??¹?。

附：英文原文

Title: Relativistic electron acceleration at the bow shock of Jupiter and beyond

Author: Raptis, Savvas, Turner, Drew L., Caprioli, Damiano, Szalay, Jamey R., Clark, George, Haggerty, Colby C.

Issue&Volume: 2026-06-03

Abstract: Collisionless shocks are ubiquitous in space plasmas throughout the Universe and are widely believed to be primary sites of cosmic ray acceleration1,2. The prevailing mechanism, diffusive shock acceleration, requires particles to repeatedly cross the shock front, gaining energy with each crossing. The maximum achievable energy is fundamentally constrained by the Hillas criterion, which relates the physical scale of the accelerator to the maximum particle energy3. However, the scarcity of direct observational constraints for acceleration sites limits our ability to predict maximum particle energies across most astrophysical systems. Here, using data from the Juno spacecraft of NASA, we show the direct evidence of relativistic electron acceleration (≥1MeV) upstream of the bow shock of Jupiter, powered by a large-scale foreshock transient4,5. Leveraging these and complementary Solar System observations, we propose a universal scaling law for the Hillas limit that empirically connects the observable size of a transient to maximum particle energy. Applying this scaling to various environments, from planetary bow shocks6 to protostellar jets7 and supernova remnants8, yields a simple model of maximum obtainable particle energies ranging from MeV scales up to about tens of GeV, and about tens of TeV, respectively, providing an observationally grounded method for constraining maximum cosmic ray energies at astrophysical shocks9,10.

DOI: 10.1038/s41586-026-10473-z

Source: https://www.nature.com/articles/s41586-026-10473-z

期刊信息

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504

官方网址：http://www.nature.com/

投稿链接：http://www.nature.com/authors/submit_manuscript.html