By Thomas Guengerich
Right: Tech professor of electrical engineering Bill Rison stands on a fence rail as he sets up a lightning sensor on Chiloe Island. The plume from the Chaiten Volcano is visible across the bay to the right of Rison.
SOCORRO, N.M., June 20, 2008 – No one said the study of volcanic lightning would be easy. A team of three New Mexico Tech researchers overcame all the minor obstacles – chickens and pigs, remoteness and a bit of rain – on a recent scientific expedition to Chile.
Two electrical engineering professors and a geophysics professor deployed an array of lightning sensors near the explosive Chaitén Volcano. They will return in a few months to collect the lightning sensors and begin analyzing the data.
Chaitén Volcano first erupted May 2, 2008, ending a period of nearly 10,000 years of dormancy. The initial eruption was one of the largest worldwide in the last decade. Immediately, the Tech team began feverishly preparing their portable sensing stations for transport to Chile.
Left: Tech professor of electrical engineering Bill Rison works on his laptop in preparation to deploying lightning sensors. He is sitting on the container used to transport the sensor. Just seconds before this picture was taken, Rison had to shoo a pig away from his gear.
Ron Thomas and Bill Rison of the Department of Electrical Engineering and volcanologist Jeffrey Johnson left the country two weeks later, hoping that the volcano would continue to erupt explosively. The team spent about two weeks in Chile setting up the sensors.
The challenges for the team included finding four cooperative landowners on Chiloé Island and Achao Island, which are about 60 kilometers from Chaitén Volcano on the mainland. The team scoped out four ideal locations and then approached those landowners.
“We were four for four,” Johnson said. “The locals were a little skeptical at first, but once we explained that we were researching the volcano, they seemed interested and happy to help.”
Right: Chickens and a dog investigate the new orange cable running through their habitat on Chiloe Island. The Tech team buried the extension cord to prevent chicken damage.
Johnson has extensive experience studying volcanoes in Central and South America, including Chile. In addition to helping the engineers deploy their sensors, he deployed his own sensors in parallel – low-frequency sound sensors that track eruptive activity from a distance.
Rison said the locals were very nice and helpful – but no one spoke English.
“It was essential to have someone to speak Spanish. Luckily we had Jeff,” Rison said. “Everything went well. The main challenge was that it was raining a lot. On our first day, we got soaked.”
Left: Tech geophysics professor Jeffrey Johnson hides his sensing equipment in the brambles to minimize the "noise" from wind.
Because transporting batteries would have been cost-prohibitive, the Tech researchers purchased batteries and chargers in the coastal city of Puerto Montt. They entered agreements with homeowners to use their electricity to keep the batteries charged. In each case, the team used a series of extension cords to deliver electricity from a home to the sensor site.
In some cases, the cords were buried to prevent chickens, pigs and dogs from eating the cables. In other cases, the cords were tied to fences.
“The island is mainly small private ranches,” Rison said. “Everybody had chickens, pigs, dogs, sheep and maybe a few cows.”
The Patagonia region of Chile is currently in the Austral winter rainy season, but the team’s efforts were only slightly disturbed by rain. The sensors – which included multiple proprietary systems – were designed to acquire data in any weather condition.
The sensing stations can store up to three months of radio wave information and are capable of running unattended.
“We’ll head back in late July or early August,” Rison said, “unless we get a major eruption before then. In that case, we’ll go right down.”
After the entire array was set up, the team collected several hours of data that included several small eruptions. At many times all the sensors detected radio signals from the small lightning in the volcanic plume.
“This is exactly what we wanted to see,” Thomas said. “It is giving more evidence that lightning is common in small eruptions even when it can't be seen visibly.”
Right: Tech physics professor Ron Thomas puts the finishing touches on the installation of a lightning sensor on a small hillock overlooking Corvovado Bay.
Rison designed the mapping sensors using field programmable gate arrays that determines the arrival time of radio waves with 40 nanosecond accuracy.
“We’ll measure the time the signals arrive at the four different stations,” physics professor Paul Krehbiel said. “From the four stations, we can determine the location and time of the lightning surges. It’s similar to triangulating.”
Krehbiel has conducted lightning research at New Mexico Tech since the 1960s. He was unable to participate in the May trip to Chile.
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 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.”
Left: The explosive eruption of Chaiten Volcano propelled tons of pumice into the atmosphere. Pumice is a volcanic rock that floats. This photo of pumice washed ashore on Chiloe Island was taken about 60 miles from the volcano.
The team set up an array of four mapping sensors that were developed by New Mexico Tech professors and students over the past 13 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.
By studying the path of lightning in a volcano’s plume, Rison and Thomas 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.”