The 2016–2017 shallow submarine eruption of Bogoslof volcano in Alaska injected plumes of ash and seawater to maximum heights of ~ 12 km. More than 4550 volcanic lightning strokes were detected by the World Wide Lightning Location Network (WWLLN) and Vaisala’s Global Lightning Dataset (GLD360) over 9 months. Lightning assisted monitoring efforts by confirming ash-producing explosions in near-real time, but only 32 out of the 70 explosive events produced detectable lightning. What led to electrical activity within some of the volcanic plumes, but not others? And why did the lightning intensity wax and wane over the lifetime of individual explosions? We address these questions using multiparametric observations from ground-based lightning sensors, satellite imagery, photographs, acoustic signals, and 1D plume modeling. Detailed time-series of monitoring data show that the plumes did not produce detectable lightning until they rose higher than the atmospheric freezing level (approximated by − 20 °C temperatures). For example, on 28 May 2017 (event 40), the delayed onset of lightning coincides with modeled ice formation in upper levels of the plume. Model results suggest that microphysical conditions inside the plume rivaled those of severe thunderstorms, with liquid water contents > 5 g m −3 and vigorous updrafts > 40 m s −1 in the mixed-phase region where liquid water and ice coexist. Based on these findings, we infer that ‘thunderstorm-style’ collisional ice-charging catalyzed the volcanic lightning. However, charge mechanisms likely operated on a continuum, with silicate collisions dominating electrification in the near-vent region, and ice charging taking over in the upper-level plumes. A key implication of this study is that lightning during the Bogoslof eruption provided a reliable indicator of sustained, ash-rich plumes (and associated hazards) above the atmospheric freezing level.

中文翻译：

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2016 年至 2017 年阿拉斯加博戈斯洛夫火山喷发期间，冰充电是否会产生火山闪电？

2016-2017 年阿拉斯加博戈斯洛夫火山的浅层海底喷发将火山灰和海水喷射到最高约 12 公里的高度。全球闪电定位网络 (WWLLN) 和维萨拉的全球闪电数据集 (GLD360) 在 9 个月内检测到超过 4550 次火山雷击。闪电通过近乎实时地确认产生灰烬的爆炸来辅助监测工作，但在 70 次爆炸事件中只有 32 次产生了可检测到的闪电。是什么导致了一些火山羽流中的电活动，而其他火山羽则没有？为什么闪电强度会在单个爆炸的整个生命周期中起伏不定？我们使用来自地面闪电传感器、卫星图像、照片、声学信号和一维羽流模型的多参数观测来解决这些问题。详细的时间序列监测数据表明，羽流在升至高于大气冻结水平（大约 - 20 °C 的温度）之前不会产生可检测的闪电。例如，在 2017 年 5 月 28 日（事件 40），闪电的延迟开始与羽状流上层模拟的冰形成相吻合。模型结果表明，羽流内部的微物理条件可与强雷暴的微物理条件相媲美，在液态水和冰共存的混合相区域，液态水含量 > 5 g m -3 并且剧烈上升气流 > 40 m s -1。基于这些发现，我们推断“雷暴式”碰撞冰充电催化了火山闪电。然而，电荷机制可能在连续介质上运行，硅酸盐碰撞在近通风口区域主导带电，和冰充电接管上层羽流。这项研究的一个关键意义是，博戈斯洛夫火山喷发期间的闪电为持续的、富含灰烬的羽流（以及相关的危害）提供了高于大气冰冻水平的可靠指标。