Abstract A period of minimum magnetic solar activity (such as June 2019) favors the observation of rare solar transient events, which would otherwise be lost in the magnetic vortex during a period of maximum solar activity, In this paper, we show that the most plausible explanation for the origin of an unexpected geomagnetic storm on June 8, 2019, is a small CME, ejected at low speed into a broad tube of an HCS on June 3, 2019, from an active region on the backside of the sun, and only detected by the STEREO Ahead Cor2 probe. The magnetic entrapment of the flux-rope and the ejecta bulk, within the co-rotating HCS (already observed with other small slow CMEs), may be responsible for the large longitudinal deflection of this CME. Several remote observations, from the SECCHI and IMPACT instruments onboard STEREO-A, as well as the predictions of several heliospheric models, favor this scenerio. We report the details of these observations.

中文翻译：

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2019 年 6 月 8 日突如其来的地磁暴和日光层流片效应

摘要 最小磁太阳活动时期（例如 2019 年 6 月）有利于观测罕见的太阳瞬变事件，否则这些事件会在太阳活动最大时期消失在磁涡旋中，在本文中，我们证明了最合理的对 2019 年 6 月 8 日意外地磁暴起源的解释是一个小型 CME，于 2019 年 6 月 3 日从太阳背面的活动区域以低速喷射到 HCS 的宽管中，并且仅由 STEREO Ahead Cor2 探头检测到。在同向旋转的 HCS 内（已经在其他小型慢 CME 中观察到），磁通绳和喷射物块的磁滞留可能是造成该 CME 大的纵向偏转的原因。来自 STEREO-A 上的 SECCHI 和 IMPACT 仪器的几次远程观测，以及几个日光层模型的预测，有利于这个场景。我们报告这些观察的细节。