Charge mechanism of volcanic lightning revealed during the 2010 eruption of Eyjafjallajokull
Charge mechanism of volcanic lightning revealed during the 2010 eruption of Eyjafjallajokull
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DOI：
10.1029/2011jb008651
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发表时间：
2011-12-14
影响因子：
3.9
通讯作者：
Burgin, Laura E.
中科院分区：
文献类型：
--
作者：
Arason, Pordur;Bennett, Alec J.;Burgin, Laura E.
几个世纪以来，火山闪电一直吸引着观察者。人们提出了几种可能的过程来解释火山羽流的带电，包括淬火岩浆-水相互作用、细粒火山灰的破裂或内摩擦以及羽流水在高空的冻结。对火山闪电的稀缺测量无法区分所提出的想法。 2010 年 4 月至 5 月冰岛埃亚菲亚德拉冰盖火山喷发可能揭示了其喷发机制。在39天的时间里，火山喷发经历了几个阶段，周围大气的条件也发生了变化，但时间不同。闪电活动最令人惊讶的变化发生在5月11日，物理喷发特征或强度没有明显变化。 5 月 3 日至 10 日期间，远程网络没有记录到闪电，随后 5 月 11 日至 20 日发生了强烈的活动。闪电活动的变化与周围大气条件的变化同时发生。此时，液滴冻结等温线的高度（约-20摄氏度）急剧下降到羽流顶部以下。因此，羽流周围的大气条件似乎正在影响甚至控制着一些闪电活动。临界羽流顶部温度似乎在埃亚菲亚德拉冰盖喷发期间开启和关闭了观测到的闪电活动，估计在 -20 到 -24 摄氏度之间。我们得出的结论是，观测到的火山闪电的显着电荷生成过程可能类似于气象雷云中的过程。
Volcanic lightning has intrigued observers through the centuries. Several likely processes have been proposed to explain the electrification of volcanic plumes, including quenching magma-water interactions, the fracturing or internal friction of fine grained ash, and the freezing of plume water at height. Scarce measurements of volcanic lightning have not been able to distinguish between proposed ideas. The Eyjafjallajokull volcanic eruption in Iceland in April-May 2010 may have revealed its charge mechanism. During its 39 days, the eruption went through a few phases while the conditions of the ambient atmosphere also changed, but at different times. The most surprising change in the lightning activity occurred on 11 May, with no obvious change in the physical eruption character or strength. During 3-10 May there was no lightning recorded by long-range networks, followed by intense activity 11-20 May. The change in lightning activity coincided with a change in the conditions of the ambient atmosphere. At this time the altitude of the isotherms for droplet freezing (about -20 degrees C) dropped drastically below the plume top. Therefore, it appears that the atmospheric conditions around the plume were influencing or even controlling some of the lightning activity. The critical plume top temperature, which appears to have turned on and off the observed lightning activity during the Eyjafjallajokull eruption is estimated to be between -20 degrees and -24 degrees C. We conclude that a significant charge generation process of the observed volcanic lightning is probably analogous to processes in meteorological thunderclouds.