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[SVC25-02] Multiphase turbulent flow explains lightning rings in volcanic plumes - Implications for the eruption sequence of the January 15, 2022, Hunga Tonga-Hunga Ha'apai eruption
★Invited Papers
Keywords:Volcanic lightning, Hunga Tonga-Hunga Ha'apai volcano, Volcanic plume simulation, Eruption monitoring
Hunga Tonga-Hunga Ha'apai (HTHH), a submarine caldera volcano of the Tonga archipelago, erupted explosively on January 15, 2022. The eruption generated the highest concentration of lightning events ever recorded, producing characteristic ring patterns of electrical discharges concentric to the vent. Here, we reproduce the key features of the observations using three-dimensional simulations of buoyant plumes in a stably stratified atmosphere.
Our numerical simulations for a buoyant plume in a linearly and weakly stratified medium under the Boussinesq approximation with heavy passive point particles have shown that the turbulent clustering mechanism works to concentrate particles in the ring-like regions of high turbulence intensity surrounding the updraft and in the umbrella cloud. A high probability of particle collisions is expected in these regions from kinetic theory. Our simulations capture the essential mechanism underlying the lightning ring observed in large volcanic eruptions, including the recent HTHH eruption.
Our minimal simulations can reproduce the observed radial expansion of the umbrella cloud as well as the oscillations of the lightning ring. The umbrella cloud and lightning ring initially expand together as proportional to time. Later, the umbrella decelerates while the lightning ring repeatedly expands and contracts around a fixed radial distance. Most remarkably, our simulation shows that expansion and contraction of the lighting ring happen even if the buoyancy flux at the source remains constant. Based on the results, we distinguish the observed lightning ring expansions due to new explosions from those due to spontaneous fluctuations. It is
inferred that the occurrence of significant explosions in several minutes around 4:51, 5:34, and 8:33 UTC on January 15, 2022, otherwise obscured by the expanding plume and umbrella cloud from the primary explosion around 4:14.
Numerical models and observations of volcanic plumes have advanced significantly in recent years, and more precise and detailed volcanic lightning data are becoming available. This study proposes a possible mechanism for the formation and evolution of lightning rings in volcanic plumes. Incorporating this mechanism into numerical models that include more realistic conditions (e.g., the presence of vapors, realistic atmospheric conditions, the supersonic injection of hot material at the source, and non-steady mass discharge) may allow estimation of eruption parameters from observations of cloud and lightning dynamics in the future. We emphasize that tracking lightning rings in volcanic plumes is particularly effective in inferring not only the opening explosive episode of a volcanic eruption but also subsequent explosive pulses during its course. For the HTHH eruption, uncovering this sequence is essential to understanding when and how disastrous events like tsunamis, damage to submarine cables, and caldera collapse occurred.
Reference:
Ichihara, M., P. D. Minini, S. Ravichandran, C. Cimarelli, and C. Vagasky (2023) Multiphase turbulent flow explains lightning rings in volcanic plumes, Comm. Earth & Environment, doi: s43247-023-01074-z.
Acknowledgements:
This research was initiated by the discussion at “Multiphase Flows in Geophysics and the Environment” program of KITP supported by the National Science Foundation under Grant No. NSF PHY-1748958.
Our numerical simulations for a buoyant plume in a linearly and weakly stratified medium under the Boussinesq approximation with heavy passive point particles have shown that the turbulent clustering mechanism works to concentrate particles in the ring-like regions of high turbulence intensity surrounding the updraft and in the umbrella cloud. A high probability of particle collisions is expected in these regions from kinetic theory. Our simulations capture the essential mechanism underlying the lightning ring observed in large volcanic eruptions, including the recent HTHH eruption.
Our minimal simulations can reproduce the observed radial expansion of the umbrella cloud as well as the oscillations of the lightning ring. The umbrella cloud and lightning ring initially expand together as proportional to time. Later, the umbrella decelerates while the lightning ring repeatedly expands and contracts around a fixed radial distance. Most remarkably, our simulation shows that expansion and contraction of the lighting ring happen even if the buoyancy flux at the source remains constant. Based on the results, we distinguish the observed lightning ring expansions due to new explosions from those due to spontaneous fluctuations. It is
inferred that the occurrence of significant explosions in several minutes around 4:51, 5:34, and 8:33 UTC on January 15, 2022, otherwise obscured by the expanding plume and umbrella cloud from the primary explosion around 4:14.
Numerical models and observations of volcanic plumes have advanced significantly in recent years, and more precise and detailed volcanic lightning data are becoming available. This study proposes a possible mechanism for the formation and evolution of lightning rings in volcanic plumes. Incorporating this mechanism into numerical models that include more realistic conditions (e.g., the presence of vapors, realistic atmospheric conditions, the supersonic injection of hot material at the source, and non-steady mass discharge) may allow estimation of eruption parameters from observations of cloud and lightning dynamics in the future. We emphasize that tracking lightning rings in volcanic plumes is particularly effective in inferring not only the opening explosive episode of a volcanic eruption but also subsequent explosive pulses during its course. For the HTHH eruption, uncovering this sequence is essential to understanding when and how disastrous events like tsunamis, damage to submarine cables, and caldera collapse occurred.
Reference:
Ichihara, M., P. D. Minini, S. Ravichandran, C. Cimarelli, and C. Vagasky (2023) Multiphase turbulent flow explains lightning rings in volcanic plumes, Comm. Earth & Environment, doi: s43247-023-01074-z.
Acknowledgements:
This research was initiated by the discussion at “Multiphase Flows in Geophysics and the Environment” program of KITP supported by the National Science Foundation under Grant No. NSF PHY-1748958.