Energy circulation in geospace lies at the heart of space weather research. In the inner magnetosphere, the steep plasmapause boundary separates the cold dense plasmasphere, which corotates with the planet, from the hot ring current/plasma sheet outside. Theoretical studies suggested that plasmapause surface waves related to the sharp inhomogeneity exist and act as a source of geomagnetic pulsations, but direct evidence of the waves and their role in magnetospheric dynamics have not yet been detected. Here, we show direct observations of a plasmapause surface wave and its impacts during a geomagnetic storm using multi-satellite and ground-based measurements. The wave oscillates the plasmapause in the afternoon-dusk sector, triggers sawtooth auroral displays, and drives outward-propagating ultra-low frequency waves. We also show that the surface-wave-driven sawtooth auroras occurred in more than 90% of geomagnetic storms during 2014–2018, indicating that they are a systematic and crucial process in driving space energy dissipation.

地球空间中的能量循环是空间天气研究的核心。在内部磁层中，陡峭的等离子体暂停边界将与行星一起旋转的冷致密等离子体球与外部的热环电流/等离子体片分开。理论研究表明，存在与剧烈不均匀性相关的等离子暂停表面波，并作为地磁脉动的来源，但尚未发现该波及其在磁层动力学中的作用的直接证据。在这里，我们使用多卫星和地面测量显示了对等离子暂停表面波及其在地磁风暴期间的影响的直接观测结果。该波在下午黄昏时分使血浆暂停振荡，触发锯齿形极光显示，并驱动向外传播的超低频波。