[M-IS09] Effects of lightning, severe weather and tropical storms

[MIS09-P03] Electrical Properties of Volcanic Lightning at Sakurajima

藤井 陽介¹、*佐藤 光輝¹、高橋 幸弘¹ (1.北海道大学 大学院理学院)

キーワード：火山雷、放電パラメタ

It is well known that the lightning discharges in volcanic plumes occur when the explosive volcanic eruption occurs. Although a large number of ground-based optical and electromagnetic observations of volcanic lightnings were conducted in the world, the electrification mechanism in the volcanic plumes and the generation mechanism of volcanic lightnings are not fully understood. Especially, the electrical properties of volcanic lightnings, such as charge amount (Q), charge moment change (Qdl), and peak current (Ip) are not fully identified, that are the key parameters to clarify the electrification mechanism and generation mechanism of volcanic lightnings. In Japan, one of the major active volcano is Sakurajima volcano, and many explosive volcanic eruptions are confirmed every year. In order to study the electrical properties of the Sakurajima volcanic lightnings, we analyzed lightning data (JLDN, WWLLN) to identify the occurrence time and location of the volcanic lightning and to estimate their peak current (Ip). We also analyzed ELF magnetic field waveform data obtained at Kuju station, Oita, to estimate charge amount (Q) and charge moment change (Qdl) of the volcanic lightnings. We analyzed Sakurajima volcanic lightnings occurred on May 12, 2017, Sep. 7, 2017, and Jan. 30, 2020, and a total of 25 volcanic lightnings are confirmed. It is found that most of these volcanic lightning were not cloud-to-ground type but in-cloud type lightning discharges and were positive polarity. It is also found that most of the volcanic lightnings have the peak current less than +20 kA. Using ELF magnetic field waveform data, we can estimate charge amount (Q) of lightning discharges, and we found that the estimated charge amount of the volcanic lightnings is mainly ranged in 0-+50 C. Using the height of the volcanic plume, we estimated charge moment change (Qdl) and found that Qdl is mainly ranged in 0-50 Ckm. At the presentation, we will show the detailed methodology to estimate Q and Qdl and will show the results derived from the data analysis.