One interpretation of the activity and magnetism of late-type stars is that these both intensify with decreasing Rossby number up to a saturation level^1,2,3, suggesting that stellar dynamos depend on both rotation and convective turbulence⁴. Some studies have claimed, however, that rotation alone suffices to parametrize this scaling adequately^5,6. Here, we tackle the question of the relevance of turbulence to stellar dynamos by including evolved, post-main-sequence stars in the analysis of the rotation–activity relation. These stars rotate very slowly compared with main-sequence stars, but exhibit similar activity levels⁷. We show that the two evolutionary stages fall together in the rotation–activity diagram and form a single sequence in the unsaturated regime in relation only to Rossby numbers derived from stellar models, confirming earlier preliminary results that relied on a more simplistic parametrization of the convective turn-over time^8,9. This mirrors recent results of fully convective M dwarfs, which likewise fall on the same rotation–activity sequence as partially convective solar-type stars^10,11. Our results demonstrate that turbulence plays a crucial role in driving stellar dynamos and suggest that there is a common turbulence-related dynamo mechanism explaining the magnetic activity of all late-type stars.

对晚型恒星的活动和磁性的一种解释是，它们都会随着Rossby数的减小而增强，直至达到饱和水平^1,2,3，这表明恒星动力取决于旋转和对流湍流⁴。然而，一些研究声称，仅旋转就足以参数化此缩放比例^5,6。在这里，我们通过在旋转-活动关系的分析中包括已演化的后主序恒星，解决了湍流与恒星动力的相关性问题。与主序恒星相比，这些恒星自转非常慢，但活动水平相似⁷。我们证明了这两个演化阶段在旋转活动图上落在了一起，并且在不饱和状态下仅与恒星模型衍生的Rossby数有关，形成了一个序列，这证实了较早的初步结果是依靠对流转弯的更简单的参数化超时时间^8,9。这反映了全对流M矮星的最新结果，后者与部分对流太阳型恒星^10、11同样处于相同的自转活动序列。我们的研究结果表明，湍流在驱动恒星动力中起着至关重要的作用，并且表明存在一种常见的与湍流有关的发电机机制，可以解释所有晚型恒星的磁活动。