Icelandic Volcanoes Serve As Lightning Research Lab
REYKJAVIK, Iceland April 20, 2010 – Icelandic volcanoes have become a field laboratory for New Mexico Tech scientists who expect to generate the clearest images ever of volcanic lightning.
| Professor Ron Thomas (kneeling) and graduate student Harald Edens install a lightning monitoring station in Iceland in recent days. Photo by Sonja Behnke/New Mexico Tech
A trio of New Mexico Tech lightning scientists arrived just before flights were cancelled and are now getting up close and personal with the erupting volcano in Iceland.
As usual with field programs, travel was somewhat difficult. The three scientists had 11 large plastic containers and a tube with antenna components. They rented the largest car available in Reykjavik, but still had to hire a taxi to transport all their equipment.
“We arrived before the travel mayhem,” Edens said. “It seems only Europe has trouble due to the ash blowing in that direction. Reykjavik, which is well west of Eyjafjallajokull, has seen no ash as far as I know.”
Electrical engineering professor Dr. Ron Thomas and two graduate students, Edens and Sonja Behnke, deployed the fourth lightning mapping stations around the volcanoes Tuesday, April 20. The team will deploy two more sensors before the end of the week. The sensing stations can store up to three months of radio wave information and will run unattended.
|Graduate student Sonja Behnke poses with a lightning sensing station in the shadow of Eyjafjallajokull in Iceland.|
The instruments track radio waves to create 3-D maps of lightning, even when they can’t see strikes. However, Thomas said that they have been able to see and photograph the lightning in Iceland.
“The eruptions on the evening of the April 18 followed one another every 15 to 20 minutes,” Edens said. “Each eruption would start as a forceful blast of ash vertically upward, followed within a couple seconds by small point-like illuminations of the ash column by intracloud lightning.”
The ash is so opaque that lightning within is invisible to the naked eye, except where it leaves the cloud boundary, creating the effect of sparkles, Eden said.
“This effect I found very intriguing,” he said. “During the more energetic eruptions in the night of April 18, I could sometimes see the lowest part of the ash column glowing cherry-red, with almost continuous (once or twice per second) tiny flashes of lightning.”
|Volcanic lightning -- as never photographed before -- at Eyjafjallajokull in Iceland. Photos by Harald Edens/New Mexico Tech|
When the ash columns grew to several kilometers in altitude, larger but less frequent lightning flashes could be seen. Some would initiate on the mountaintop or lava fountain and propagate upward; others appeared to initiate in the cloud. On rare occasions the lightning jumped out of the ash column to strike the mountaintop, much like a "bolt from the blue" in a regular thunderstorm. After 10 to 15 minutes, when an eruption would be over, infrequent but extensive flashes would illuminate the downwind drifting ash cloud. Usually there was only one of such a flash per eruption.
Eyjafjallajokull – which is Icelandic for “island mountain glacier” – first erupted March 20, when a fissure opened on the eastern side of the mountain. That first series of seismic events occurred in an area that was not covered by ice, therefore did not create a dramatic plume of smoke and ash.
The Tech scientists assembled their equipment and arrived in Iceland on Wednesday, April 14. By that time, the initial fissure eruptions had died down, but the new explosive eruptions started that day. The second round of eruptions occurred in an area covered by glaciers.
Behnke said the Icelandic people have been very receptive to hosting our instruments. The local people who are hosting the instruments are mostly farmers and have been receptive to outsiders studying their volcanoes. On several occasions, the locals have invited the Tech scientists into their homes for food and drink.
“The interaction of the magma with the ice makes for a very explosive eruption,” Behnke wrote via e-mail.
Behnke said many of the Icelandic people are worried about ash fall and the consequences. In some areas, farmers and other residents have been evacuated. Others, she wrote, are enjoying the lightning show above Ejyafjallajokull. She said scientists expect the neighboring volcano, Katla, to erupt in the near future as well.
“We learned that, historically, every time Eyjafjallajokull has erupted (which is infrequent), the neighboring volcano, Katla has also erupted,” she wrote. “Katla is also under a glacier and when it erupts, it erupts in a big way. The last time Katla erupted in 1918 it made lots of lightning.”
The Tech lightning team has plenty of experience chasing volcanoes. They set up the Lightning Mapping Array at Mt. St. Augustine in Alaska with two sensing stations in 2006. They set up three sensing stations at Chaiten Volcano in May 2008. They deployed four sensing stations at Mount Redoubt in Alaska in January 2009. With six sensing stations in Iceland, the team expects to assemble the clearest 3-D images of volcanic lightning ever. The Tech lightning research is funded by a multi-year grant from the National Science Foundation.
Edens wrote that the upward lightning he saw April 18 supports LMA observations from the 2006 Mt. St. Augustine eruption in Alaska.
Because they only had two instruments deployed in 2006, the Tech team did not have altitude information. However, due to a fluke of nature they could deduce rough altitudes. The fluke was truly a fortuitous accident. At Mt. St. Augustine, one of the instruments caught two signals; the radiowaves bounced off the surface of the bay, giving the team three signals. By combining the three signals, they concluded that one flash of lightning was propagating upward, initiated at the mountaintop.
“Now we have seen and photographed this in the Eyjafjallajokull eruption,” Edens said.
The radio waves created by lightning travel about one foot per nanosecond. With equipment that captures information every 40 nanoseconds, the sensors will be able to pinpoint a three-dimensional location of lightning within about 40 feet, Krehbiel said.
“We measure the time the signals arrive at the different stations,” said physics professor Dr. Paul Krehbiel, who collaborated with Thomas and Dr. Bill Rison to design, program and build the first Lightning Mapping Array. “We can determine the location and time of the lightning surges. It’s similar to triangulating.”
The mapping sensors were developed by New Mexico Tech professors and students over the past 15 years. Tech’s pioneering research into lightning – both volcanic and thunderstorm lightning – has led to a series of breakthroughs, including proprietary sensing technology that allows scientists, meteorologists and storm chasers to pierce the veil of clouds to “see” lightning as it occurs.
“We receive radio bursts of noise generated from sparks of lightning, just like the static you hear on your car radio during a thunderstorm,” Thomas said. “We will use our sensing stations to locate the lightning and track its path.”
By studying the path of lightning in a volcano’s plume, scientists hope to gather an understanding of how electrical activity is transmitted from the Earth into the atmosphere.
“With each lightning flash, we’ll be able to monitor how it moves through the clouds and where it goes,” Thomas said. “If we take all our theories about lightning created in thunderstorms, we can learn about both types of lightning.”
– NMT –
By Thomas Guengerich/New Mexico Tech