We report a rare regime of Earth's magnetosphere interaction with sub-Alfvénic solar wind in which the windsock-like magnetosphere transforms into one with Alfvén wings. In the magnetic cloud of a Coronal Mass Ejection (CME) on 24 April 2023, NASA's Magnetospheric Multiscale mission distinguishes the following features: (a) unshocked and accelerated low-beta CME plasma coming directly against Earth's dayside magnetosphere; (b) dynamical wing filaments representing new channels of magnetic connection between the magnetosphere and foot points of the Sun's erupted flux rope; (c) cold CME ions observed with energized counter-streaming electrons, evidence of CME plasma captured due to by reconnection between magnetic-cloud and Alfvén-wing field lines. The reported measurements advance our knowledge of CME interaction with planetary magnetospheres, and open new opportunities to understand how sub-Alfvénic plasma flows impact astrophysical bodies such as Mercury, moons of Jupiter, and exoplanets close to their host stars.

中文翻译：

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2023 年 4 月日冕物质抛射驱动地球的阿尔文翼


我们报告了一种罕见的地球磁层与亚阿尔芬太阳风相互作用的情况，其中风向袋状磁层转变为具有阿尔芬翼的磁层。在 2023 年 4 月 24 日日冕物质抛射 (CME) 的磁云中，美国宇航局的磁层多尺度任务具有以下特征：(a) 无冲击且加速的低 β CME 等离子体直接撞击地球的白天磁层； (b) 动力翼细丝代表磁层和太阳喷发磁通绳足点之间磁连接的新通道； (c) 用激发的逆流电子观察到的冷 CME 离子，这是由于磁云和阿尔文翼场线之间的重新连接而捕获 CME 等离子体的证据。报告的测量结果增进了我们对日冕物质抛射与行星磁层相互作用的了解，并为了解次阿尔弗尼等离子体流如何影响水星、木星卫星和靠近其主恒星的系外行星等天体物理天体提供了新的机会。