The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed¹.

地球的磁层是地球空间系统的最外层，它使高能带电粒子从太阳和太阳风中偏转。太阳风对地球的磁层有重大影响，但尚不清楚太阳耀斑是否同样适用——太阳上突然爆发的电磁辐射。在这里，我们使用最近开发的整个地球空间模型，结合 2017 年 9 月 6 日 X9.3 太阳耀斑事件的观测数据，揭示太阳耀斑对磁层动力学以及磁层与其相邻电离层（地球电离层的电离部分）之间的电动耦合的影响。高层大气。我们观察到在 90 公里到 150 公里的高度上，极地电离层 E 区的耀斑引起的光电离迅速且大幅度增加。这降低了白天太阳风-磁层相互作用中机械能转换的效率，导致地球上层大气的焦耳加热减少，磁层对流的重新配置，以及白天和夜晚极光降水的变化。因此，这项工作表明，太阳耀斑效应通过电动耦合延伸到整个地球空间，并且并不像以前认为的那样局限于吸收辐射能量的大气区域¹ .