Volcanic Ash Affected by Lightning During the Hunga 2022 Eruption

The 15 January 2022 eruption of Hunga volcano (Kingdom of Tonga) produced the most lightning ever documented during an explosive eruption to date. This study estimates the mass of erupted tephra that may be structurally or electromagnetically affected by the lightning, based upon lightning peak current, channel length, and ash plume particle concentration. The lightning channels totaled 1.67 million m 3 in volume and contained 548 kg of volcanic ash at a calculated plume concentration of 0.328 g/m 3 . From this total, 54.8 kg of ash may display physical evidence in the form of lightning‐induced textures, such as lightning‐induced volcanic spherules, but this is an insignificant fraction of the total airfall deposit (10 −8 %). However, the total mass of ash exposed to magnetic flux densities exceeding Earth's ambient surface values is 2.24 × 10 14 g, corresponding to just over a third (34.9%) of the calculated mass of total airfall (5.21 × 10 14 g). This study reveals that even though physical evidence of volcanic lightning may be limited, ash particles will still be affected by the electromagnetic fields generated by the lightning discharge. The extent of these effects will be a function of lightning properties, ash properties, and location of the ash in relation to the discharge channel.