Surveys in Geophysics

, Volume 27, Issue 4, pp 387–432

Electrification of volcanic plumes

Original Paper

DOI: 10.1007/s10712-006-9007-2

Cite this article as:
Mather, T.A. & Harrison, R.G. Surv Geophys (2006) 27: 387. doi:10.1007/s10712-006-9007-2

Abstract

Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity.

Keywords

Volcanic lightning Atmospheric electricity Historical accounts of volcanic lightning Origins of life Volcanic monitoring Ash-charging mechanisms Planetary lightning Planetary volcanism Ash fall-out Global atmospheric electrical circuit Volcanoes and climate Hazards 

Nomenclature

A

Ion asymmetry parameter, A = n+μ+/nμ

a,b

Vertical distances

e

Magnitude of the elementary charge (1.6 × 10−19 C)

EFW

Vertical electric field in fair weather conditions (EFW =  − PG)

Ep

Vertical electric field associated with a region of charge

j

Number of elementary charges

i

Polarity of the ion

k

Boltzmann’s constant (1.38 × 10−23 J K−1)

n, n+, n

Number concentration of total ions, positive ions and negative ions

Nj

Number concentration of particles carrying j elementary charges

N0

The number of neutral particles, i.e., number of particles with j = 0

PG

Potential gradient. The rate of change of electric potential with vertical distance, usually referred to a measurement made at 1 m above the surface. When the potential increases positively with height, the PG is considered positive

Q

Electric charge

r

Particle radius

T

Temperature

x

Horizontal distance

X

Ion–aerosol attachment rate

Z

Aerosol particle number concentration

βij(r)

Attachment coefficient of ion (sign i =  ± 1) to a particle of radius r carrying j charges

ɛ0

Permittivity of free space \(\left({\frac{1}{36\pi\times10^9}}\right)\) F m−1

ϕ

Electric potential

μ+, μ

Ion mobility (drift speed in a unit electric field)

J

Mean number of elementary charges per particle

τ

Charging timescale

Rc

Columnar resistance, the resistance of a unit column of atmosphere from the surface to the ionosphere

VI

Ionospheric potential

Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  1. 1.Department of Earth SciencesUniversity of OxfordOxfordUK
  2. 2.Department of MeteorologyThe University of ReadingReadingUK

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