The Volcanic Lightning Research Project
A collaborative study by New Mexico Tech and the Alaska Volcano Observatory
Sponsored by the U.S. National Science Foundation
and the Alaska Volcano Observatory of the University of Alaska
This is a research project by New Mexico Tech and the Alaska Volcano
Observatory (AVO) at the University of Alaska, sponsored by the
U.S. National Science Foundation. It is an extension of our research
studies of thunderstorms. The principal investigators at New Mexico
Tech are Ronald Thomas, Paul Krehbiel, and William Rison. The principal
investigator at the University of Alaska is Stephen McNutt.
It has long been known that volcanic eruptions can produce spectacular
lightning. However, very little has otherwise been known about volcanic
lightning, and few scientific studies have been conducted of this very
interesting phenomena. It is logistically difficult and dangerous to study
active volcanoes, and scientific equipment for documenting and investigating
volcanic lightning in remote locations has only recently been developed.
Studies of volcanic lightning have both scientific and practical interest.
The scientific issues include the questions of how volcanic plumes and
clouds become electrified and the similarities and differences with the
incidence of lightning in thunderstorms. The measurement techniques we
use detect lightning and electrical activity remotely, both inside the
volcanic cloud and in inclement weather conditions when visual observations
are not possible. Thus the occurrence of an eruption could be confirmed in
remote locations and in poor weather conditions. Locating the lightning in
the drifting plume can show the location of the ash plume. Measurement of
lightning and electrical activity can be another tool to help understand
the processes occurring during an eruption. Volcanic lightning is also
an additional, often unexpected hazard of eruptions.
How we detect and locate the lightning and electrical activity
We use simple radio receivers to listen for the static that can often be
heard on a car radio during a thunderstorm. The static hiss from a single
lightning flash consists of many thousands of impulses generated by the
lightning. Modern technology allows us to accurately measure the time
each impulse arrives at a measurement station. From the arrival times
at several stations we can determine the locations of the radio impulses.
We use this technology to map out the structure and extent of the complete
lightning activity in thunderstorms and are now applying it to the study
of volcanic lightning. The systems we have developed for doing this are
called Lightning Mapping Arrays (LMAs) and utilize specially designed
electronics and GPS receivers to record the arrival times and signal
strength at each station. The different stations of a network passively
listen for the radio signals in a locally unused VHF televison channel,
most often Channel 3. The stations are lightweight and portable, enabling
them to be transported and set up relatively rapidly for field studies.
The Redoubt Network
Redoubt started to re-awaken on Sunday January 25, 2009. Having been
alerted to the onset of seismic activity by AVO, and starting with a list
of possible measurement sites previously scouted out by AVO, we quickly
moved to transport and deploy four lightning mapping stations along
the Kenai coast on the opposite site of Cook Inlet from Redoubt. By the
following Saturday four stations were set up and recording data. The last
eruption of Redoubt was in 1989/1990 and began within 24 hours of becoming
seismically active. This time Redoubt provided 2 months advance notice,
giving us time to finalize the network and to set up internet connections
for monitoring its operation. The stations are set up at Ninilchik,
Clam Gulch, on Kalifornsky Beach (K-Beach) south of Kenai/Soldotna, and
at Nikiski. The spread of the stations enable us to obtain good locations
of the lightning activity. All stations have a good view of Redoubt.
At three of the four stations, the VHF radio antenna is situated on the
edge of the high coastal bluff overlooking Cook Inlet. These stations receive
each lightning signal both by direct line of sight and by being reflected from
the water surface of Cook Inlet. The interference effects between the
direct and reflected signals will enable us to better measure the altitude
of the lightning activity. A similar network and and measurment approach
was set up in the Homer/Anchor Point area in January 2006 in a successful
study of the Mt. Saint Augustine eruption.
To begin with, we are looking primarily at the received signal amplitudes
and widths versus time. From the previous Augustine study, this tells us
quite a bit about what the volcano is doing electrically. Complete
processing of the four-station data to obtain the locations and structure
of the lightning discharges will follow.
We have obtained measurements of several other volcanic eruptions. Our first
measurements were of the 2006 eruption of Mt. Saint Augustine, an island
volcano on the far south side of Cook Inlet. We set up two stations
near Homer and in Anchor Point in time for the final explosive eruptions
on January 28, 2006. The first of these eruptions produced substantial
lightning and was the subject of a Brevia article in Science magazine.
Two additional stations were subsequently added on the opposite side of Cook
Inlet, closer to Augustine, but the volcano had quieted down by that time.
The Augustine deployments provided excellent data and experience for our
In May and June of 2008 Ron Thomas, Bill Rison and vulcanologist Jeff
Johnson of New Mexico Tech deployed four lightning mapping stations and
related instruments off the mainland coast of Southern Chile to observe the
electrical activity of the major Chaiten volcanic eruption. The stations
were set up about a month after the initial, huge and completely unexpected
explosion of Chaiten. We thus missed the spectacular lightning associated
with the volcano's initial and Chaiten's early activity. However, even
a month afterward the volcano continued to have electrical activity,
producing occasional, smaller lightning discharges. In December 2007
vulcanologist colleagues Bill McIntosh and Nelia Dunbar and students
from NM Tech deployed two LMA stations at 13,000 feet altitude on the rim
overlooking the active lava lake of the Mt. Erebus volcano in Antarctica.
These measurements detected small sparks being produced during explosive gas
eruptions at the surface of the lava lake .
Results So Far
The Redoubt observations are very similar to those seen from Augustine.
Essentially continuous sparking and electrical activity is observed
during the explosive phase of the eruption, followed after a few minute
delay by the onset of discrete lightning discharges in the cloud and
downwind plume from the explosion. The plume activity often continues
for several tens of minutes or longer, initially being extremely active
and then increasingly intermittent with time before finally dying out.
The plume discharges are as large and energetic as those seen in large,
fully-developed thunderstorms. The difference between Redoubt and Augustine
is that the Redoubt explosions have been much more numerous and long-lived,
and also have produced substantially more lightning. In addition we have
been capturing the complete sequence of eruptive activity, from the very
initial explosive eruption sequence to the subsequent, longer-duration
eruptions. We should also see the electrical activity from pyroclastic
flows, dome-building/collapse events, through the eventual decay of the
eruption. The most recent previous eruption of Redoubt was in 1989-90 and
lasted 5 months!