Many years back, I attended a special session on Elves, Sprites and Blue Jets at AGU in San Francisco.
These are typically observed above severe thunderstorm clouds and are observed at something like 100km altitude (magnetosphere).
Explosive volcanic eruptions often occur through a lake or the sea (eg. Rose et al 1995), and can also entrain 100-1000s MTons of water vapour from the boundary layer for atmospheric moisture when extensive pyroclastic density currents are generated and source the ashcloud (eg. 15 June 1991 Pinatubo; Dartevelle et al 2002) .
All such eruptions are rich in water vapour.
Rapidly during ash cloud ascent water vapour condenses on ash particles.
Then freeze over to form snowflakes and ice particles (eg. Rabaul 1937, Surtsey 1963, Pinatubo 1991, Vulcan 1994, Montserrat Boxing Day cloud, Hekla 2000, Eyjafjallajokull 2010...; eg. Durant et al 2008 and refs therein) .
In this way, the eruption cloud turns into some kind of severe thunderstorm or generates one, whichever way one wishes to look at it.
Meteorological severe storms generate electricity.
One can expect that severe storms associated with volcanic explosive eruptions will generate electricty using the same electrification mechanisms as your standard thunderstorm.
In addition to those electrification mechanisms associated with normal thunderstorms, however, when magma is fragmented into ash, additional electrification occurs during explosive volcanic eruptions and especially in phreatomagmatic éruptions as a result of fracto-emission (Gilbert and Lane 1994, etc...).
Electrification (charge generation, charge separation and "dipole" system development) from fracto-emission is consistent with field measurements of the electric field during volcanic explosive éruptions (eg. Sakurajima; Gilbert et al 1992) and with lightning detection during explosive eruptions.
Explosive volcanic eruptions commonly reach ascent heights that are similar or higher than severe thunderstorms, exceeding 15-20km elevation above the ground. Indeed numerous VEI 3 eruption clouds are detected by remote sensing colleagues each year (eg. Rose et al 2000).
Hence, with similar thermal energy fluxes (correlated with ascent height) and expected more intense electrification than severe thunderstorms, phreato-subplinian or phreatoplinian explosive eruptions can be expected to generate phenomena such as elves, blue jets and sprites into the magnetosphere directly above the volcanic eruption cloud.
But I am not aware of anyone who would have made any measurements to assess this hypothesis in the atmospheric science community?
I am curious to find out if anyone knows more about this since I first queried atmospheric experts on elves, sprites and blue jets above standard thunderstorms more than 20 years back ?
Cheers,
Gerald
Hello Mark,
Thank you for the response.
First I'd like to correct a gigantic typo I've made.
Blue jets, sprites and elves are observed in the ionosphere (I typed magnetosphere, instead of ionosphere; "magnetosphere" is meaningless in the context here).
Second, thunderstorms above which such phenomena have been observed, from space, correspond to what volcanologists refer to as VEI 3 éruptions (in terms of intensity-scale).
If I am not mistaken, such eruptions are not rare in the sense that 60 such eruptions are detected and tracked using satellite (and radar imagery) each year. Most of these are also detected and tracked using remote sensing and other monitoring techniques from the ground.
They are quite a matter for attention as they are the most common hazardous eruptions occuring each year on the planet.
They pose a diversity of hazards.
First they are the most common volcanic hazard to international air traffic. They have already incurred huge economic impacts to the international air traffic industry and to society at large (more than 300 ashcloud - airplane encounters since 1980 or so; tens of severely damaging encounters)
Second, the fallout of material (ash, pumice etc..) can accumulate on the roofs of buildings and roof collapse can occur (eg. the major Harbour town of Rabaul, PNG, was completely flattened during the 19 Sept 1994 eruption).
As eruptions trigger their own thunderstorms and as eruptions often occur within the subtropics, rainfall and increased runoff on impervious ash leads to devastating mudflows. Fine ash is also a health hazard to people and animals and ash and aérosols from volcanoes can also deveastate crops and natural ecosystems...
Third, they are often associated with pyroclastic density currents, equally devastating potentially.
VEI3 eruptions typically generate volcanic clouds rising 10 to 20 km above sea-level.
So in terms of thermal energy flux, they are expected to match thunderstorms.
In sum, if elves, sprites and blue jets are observed above normal thunderstorms, they should also be observed above VEI3 eruption clouds.
Such volcanic eruption clouds are not at all rare.
Observing such phenomena would enable to relate them to eruption cloud parameters (electrification, mass loading of water and ice particles, mass loading of ash and aerosols ?) and the comparison between these phenomena arising from normal thunderstorms and from volcanic eruption clouds could be a novel way to advance the understanding of elves, sprites and blue jets.
Truly I can see no reason why they would not have been detected or studied above volcanic eruption clouds, not to mention that first detection of those sprites etc. would assure a milestone Nature or Science paper to the discoverers (publication opportunities generally).
Finally, when the volcanology and atmospheric sciences have worked together, great advances in understanding have resulted.
In the end, the question remains. I hope someone might have the answer ?
And if not, as you say, I share the view that this would make an exciting cross-disciplinary research proposal.
Perhaps if this work has not been carried out, an insightful question would also be why not ?
All the best,
Gerald
Gerald -
You might try contacting Steve McNutt at the University of Florida. I know he was exploring the development of lightening in volcanic ash clouds when he was at the Geophysical Institute (Univ. of Alaska Fairbanks). This is the same place where some of the fundamental discoveries re: sprites and jets were first made in the early/mid '90's, so Steve would likely be familiar with the phenomenon.
Good luck!
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