The ‘middle corona’ is a critical transition between the highly disparate physical regimes of the lower and outer solar coronae. Nonetheless, it remains poorly understood due to the difficulty of observing this faint region (1.5–3 R_☉). New observations from the Solar Ultraviolet Imager of a Geostationary Operational Environmental Satellite in August and September 2018 provide the first comprehensive look at this region’s characteristics and long-term evolution in extreme ultraviolet. Our analysis shows that the dominant emission mechanism here is resonant scattering rather than collisional excitation, consistent with recent model predictions. Our observations highlight that solar wind structures in the heliosphere originate from complex dynamics manifesting in the middle corona that do not occur at lower heights. These data emphasize that low-coronal phenomena can be strongly influenced by inflows from above, not only by photospheric motion, a factor largely overlooked in current models of coronal evolution. This study reveals the full kinematic profile of the initiation of several coronal mass ejections, filling a crucial observational gap that has hindered understanding of the origins of solar eruptions. These new data uniquely demonstrate how extreme ultraviolet observations of the middle corona provide strong new constraints on models seeking to unify the corona and heliosphere.

“中日冕”是下日冕和外日冕高度不同的物理状态之间的关键过渡。尽管如此，由于难以观察这个微弱的区域（1.5-3 R _☉），它仍然知之甚少 ）。地球静止运行环境卫星的太阳紫外线成像仪在 2018 年 8 月和 2018 年 9 月进行的新观测首次全面了解了该地区的特征和极紫外线的长期演变。我们的分析表明，这里的主要发射机制是共振散射而不是碰撞激发，这与最近的模型预测一致。我们的观察结果表明，日球层中的太阳风结构源于中日冕中表现出的复杂动力学，而这些动力学不会发生在较低的高度。这些数据强调，低日冕现象可能会受到来自上方的流入的强烈影响，而不仅仅是光球运动，这是当前日冕演化模型中很大程度上被忽视的因素。这项研究揭示了几次日冕物质抛射开始的完整运动学特征，填补了阻碍对太阳爆发起源理解的关键观测空白。这些新数据独特地证明了对中日冕的极紫外观测如何为寻求统一日冕和日球层的模型提供了强有力的新限制。