Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions
Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions
复制标题
DOI：
10.1002/2017jd027990
复制
发表时间：
2018-04-27
影响因子：
4.4
通讯作者：
Cigala, V.
中科院分区：
文献类型：
--
作者：
Behnke, S. A.;Edens, H. E.;Cigala, V.
对火山闪电的研究表明，与火山爆发有关的一种相对持久的甚高频辐射源与闪电产生的辐射不同。这种非常高频率的信号由于其持久的性质而被称为连续射频（CRF）。产生这种信号的放电机制先前被假设是由火山口附近大量的小型（10- 100米）先导形成放电引起的。为了验证这一假设，从2015年5月至6月收集了日本樱岛火山爆发期间发生的电气和火山活动的多参数数据集。我们的观测结果表明，一个单一的CRF脉冲的持续时间为160纳秒的顺序（给出的上限放电长度为10米），是不同的近喷口闪电放电的顺序为30米的长度。CRF脉冲没有产生明显的电场变化，并发生在没有净静电场。闪电映射数据和红外视频观测的喷发柱表明，CRF脉冲起源于气体推力区的柱。这些观察表明，CRF脉冲不是由小的，形成领导者的放电，而是更类似于流光放电，可能在几米的长度。简单的语言摘要本文探讨了起源的无线电频率（RF）信号以前被称为连续的RF已被检测到的火山爆发的火山灰羽流。持续的射频被假设是由许多非常小的闪电状放电引起的，大约100米长，发生在火山口。为了验证这一假设，我们在日本樱岛火山进行了多参数观测实验。我们在2015年樱岛火山喷发期间测量了持续的RF，发现持续的RF是持续时间短的RF脉冲的集合，持续时间约为160 ns。这些RF脉冲与通常由闪电产生的RF脉冲不同。我们还观察到小的，30米的闪电放电发生在火山口附近，与连续RF的来源不同。我们的观察表明，连续的射频是由放电引起的，这种放电甚至比非常小的（大约100米）闪电放电更简单。我们的结论是，连续的射频是由大量的，小的，类似于流光放电的放电，在几米长的顺序。
Volcanic lightning studies have revealed that there is a relatively long-lasting source of very high frequency radiation associated with the onset of explosive volcanic eruptions that is distinct from radiation produced by lightning. This very high frequency signal is referred to as continual radio frequency (CRF) due to its long-lasting nature. The discharge mechanism producing this signal was previously hypothesized to be caused by numerous, small (10-100m) leader-forming discharges near the vent of the volcano. To test this hypothesis, a multiparametric data set of electrical and volcanic activity occurring during explosive eruptions of Sakurajima Volcano in Japan was collected from May to June 2015. Our observations show that a single CRF impulse has a duration on the order of 160ns (giving an upper limit on discharge length of 10m) and is distinct from near-vent lightning discharges that were on the order of 30m in length. CRF impulses did not produce discernible electric field changes and occurred in the absence of a net static electric field. Lightning mapping data and infrared video observations of the eruption column showed that CRF impulses originated from the gas thrust region of the column. These observations indicate that CRF impulses are not produced by small, leader-forming discharges but rather are more similar to a streamer discharge, likely on the order of a few meters in length.Plain Language Summary This paper investigates the origin of a radio frequency (RF) signal previously termed continual RF that has been detected from the ash plumes of explosive volcanic eruptions. Continual RF had been hypothesized to be caused by many very small lightning-like discharges on the order of 100m in length occurring at the vent of the volcano. To test this hypothesis, we conducted a multiparametric observational experiment at Sakurajima Volcano in Japan. We measured continual RF during eruptions of Sakurajima in 2015 and found that continual RF is a collection of short duration RF impulses, on the order of 160ns in duration. These RF impulses are distinct from those typically produced by lightning. We also observed small, 30-m lightning discharges occurring near the volcanic vent that were distinct from the source of continual RF. Our observations show that continual RF is caused by an electrical discharge that is more simple than even a very small (approximate to 100m) lightning discharge. We conclude that continual RF is caused by numerous, small, electrical discharges similar to streamer discharges, on the order of a few meters in length.