Physical properties of volcanic lightning: Constraints from magnetotelluric and video observations at Sakurajima volcano, Japan

Koki Aizawa, Corrado Cimarelli, Miguel A. Alatorre-Ibargüengoitia, Akihiko Yokoo, Donald B. Dingwell, Masato Iguchi

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


The lightning generated by explosive volcanic eruptions is of interest not only as a promising technique for monitoring volcanic activity, but also for its broader implications and possible role in the origin of life on Earth, and its impact on the atmosphere and biosphere of the planet. However, at present the genetic mechanisms and physical properties of volcanic lightning remain poorly understood, as compared to our understanding of thundercloud lightning. Here, we present joint magnetotelluric (MT) data and video imagery that were used to investigate the physical properties of electrical discharges generated during explosive activity at Sakurajima volcano, Japan, and we compare these data with the characteristics of thundercloud lightning. Using two weeks of high-sensitivity, high-sample-rate MT data recorded in 2013, we detected weak electromagnetic signals radiated by volcanic lightning close to the crater. By carefully inspecting all MT waveforms that synchronized with visible flashes, and comparing with high-speed (3000 frame/s) and normal-speed (30 frame/s) videos, we identified two types of discharges. The first type consists of impulses (Type A) and is interpreted as cloud-to-ground (CG) lightning. The second type is characterized by weak electromagnetic variations with multiple peaks (Type B), and is interpreted as intra-cloud (IC) lightning. In addition, we observed a hybrid MT event wherein a continuous weak current accompanied Type A discharge. The observed features of volcanic lightning are similar to thunderstorm lightning, and the physical characteristics show that volcanic lightning can be treated as a miniature version of thunderstorm lightning in many respects. The overall duration, length, inter-stroke interval, peak current, and charge transfer all exhibit values 1-2 orders of magnitude smaller than those of thunderstorm lightning, thus suggesting a scaling relation between volcanic and thunderstorm lightning parameters that is independent of the type of charged particles. On the other hand, the polarities, which are estimated by long-time (3.4 yrs) MT (32 samples/s) and video (30 frame/s) observations, are different than those of normal thunderstorm lightning. These observations are consistent with the notion that charge structures in volcanic ash plumes are highly disordered and are characterized by numerous small charged regions with high charge density.

Original languageEnglish
Pages (from-to)45-55
Number of pages11
JournalEarth and Planetary Science Letters
Publication statusPublished - Jun 15 2016

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'Physical properties of volcanic lightning: Constraints from magnetotelluric and video observations at Sakurajima volcano, Japan'. Together they form a unique fingerprint.

Cite this