We discuss Wind observations of a long and slow magnetic cloud (MC) propagating through large‐amplitude Alfvén waves (LAAWs). The MC axis has a strong component along GSE X , as also confirmed by a Grad‐Shafranov reconstruction. It is overtaking the solar wind at a speed roughly equal to the upstream Alfvén speed, leading to a weak shock wave 17 hr ahead. We give evidence to show that the nominal sheath region is populated by LAAWs: (i) a well‐defined de Hoffmann‐Teller frame in which there is excellent correlation between the field and flow vectors, (ii) constant field and total pressure, and (iii) an Alfvén ratio (i.e., ratio of kinetic‐to‐magnetic energy of the fluctuations) near unity at frequencies much lower than the ion cyclotron frequency in the spacecraft frame. In the region where the LAAWs approach the MC's front boundary there are field and flow discontinuities. At the first, magnetic reconnection is taking place, as deduced from a stress balance test (Walén test). This severs connection of some field lines to the Sun and the solar wind strahl disappears. There follows a 2‐hr interval where the magnetic field strength is diminished while pressure balance is maintained. Here the bidirectionality of the suprathermal electron flows is intermittently disrupted. This interval ends with a slow expansion fan downstream of which there is a dropout of halo electrons just inside the front boundary of the MC. This study illustrates an untypical case of a slow MC interacting with LAAWs in the slow solar wind.

中文翻译：

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通过大振幅Alfvén波传播的磁云的研究

我们讨论了通过大振幅Alfvén波（LAAW）传播的长而慢的磁云（MC）的风观测。MC轴沿着GSE X具有很强的分量也由Grad-Shafranov重建所证实。它以大约等于上游Alfvén速度的速度赶上了太阳风，导致前方17小时的冲击波微弱。我们提供证据表明标称鞘管区域由LAAW填充：（i）定义明确的de Hoffmann-Teller框架，其中场和流矢量之间具有极好的相关性；（ii）恒定场和总压力，以及（iii）在远低于航天器框架中离子回旋加速器频率的频率下，Alfvén比（即波动的动磁能比）接近于一。在LAAW接近MC的前边界的区域中，存在场和流的不连续性。首先，根据应力平衡测试（Walén测试）推断，发生了磁重连接。这样就切断了一些磁场线与太阳的连接，而太阳风也消失了。随后是2小时的间隔，在此间隔内磁场强度会降低，而压力平衡会保持不变。在这里，超热电子流的双向性被间歇性破坏。此间隔以一个慢速扩展风扇结束，在其下游，MC的前边界内恰好有一个卤素电子丢失。这项研究说明了慢速MC与慢速太阳风中的LAAW相互作用的非典型情况。此间隔以一个慢速扩展风扇结束，在其下游，MC的前边界内恰好有一个卤素电子丢失。这项研究说明了慢速MC与慢速太阳风中的LAAW相互作用的非典型情况。此间隔以一个慢速扩展风扇结束，在其下游，MC的前边界内恰好有一个卤素电子丢失。这项研究说明了慢速MC与慢速太阳风中的LAAW相互作用的非典型情况。