SOCORRO, N.M. March 8, 2011– New Mexico Tech doctoral student Sonja Behnke won the Outstanding Student Presentation Award for her work analyzing volcanic lightning in Alaska.
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Sonja Behnke at work in her office on campus.

Sonja Behnke explains her poster, which is now in the second floor hall of Workman Center.

Behnke won the award from the Atmospheric and Space Electricity focus group at the American Geophysical Union conference in December in San Francisco.

Tech professor Dr. Richard Sonnenfeld said the judges had little debate over the impact of Behnke’s work.

“The judging at AGU is very competitive, and there is lots of arguing back and forth about the relative merits of various papers,” Sonnenfeld said. “Sonja’s nomination was one of the least contentious. It was obvious to all the judges that she is doing ground-breaking work, and she presents her results clearly and with some flair.”

Behnke presented her poster, “The Life Cycle of Redoubt's Volcanic Lightning Storms,” which explains how lightning discharges changed over time during the 2009 eruptions of Mt. Redoubt in southeast Alaska.

“There is a dramatic difference in electrical activity between early and late phases of a single explosive eruption,” Behnke said. “During the explosive phase, we saw strong signals from low altitude: small in duration, short in length – about 100 meters – and right above the volcano.”

About 5 minutes after the onset of the explosive eruption, electrical activity starts in the plume.  The lightning, during this “plume phase” becomes less frequent, but the discharges become larger.

“Over time, it looks like horizontally-stratified charge layers develop, like a thunderstorm,” she said. “In a thunderstorm there are typically two or three charge layers, and we see in these volcanic lightning storms it takes at least 10-15 minutes to get to a similar structure.”

Behnke hopes to help develop a better explanation of how volcanic eruptions trigger lightning as part of an effort to understand the relationship between volcanic activity and electrical activity.

“I’m interested in the applications of using lightning to monitor volcanoes,” she said. “People who are interested in the dynamics of the plume might also be interested in using lightning to understand what’s happening in the plume.”

Behnke earned her bachelor’s in physics at New Mexico Tech in 2003. After four years of working, she returned to Tech to enter a doctoral program in 2007. Since then, she’s helped deploy the Lightning Mapping Array in Alaska and in Iceland.

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Volcan Chaiten in Chile produced dramatic lightning flashes during the explosives phase of eruption. Sonja Behnke and other New Mexico Tech researchers are at the forefront of studying this phenomenon.

Her latest work relates to her trip to Alaska, which involved research at Mt. Redoubt in 2009. Her next projects will examine data gathered in Iceland in 2010.

The life of a physics graduate student is not all adventure and excitement, however.

“I spend 90 percent of my time in front of a computer,” she said. “I was in Iceland for two weeks in 2010, and had 50 weeks at my computer.”

The Lightning Mapping Array records and time-stamps radio signals generated by lightning flashes. Processing the data from Iceland took a full month. Once the raw data is generated, Behnke uses customized programs and writes new code to analyze the data.

“I spent weeks looking at data, stepping through it – second by second, or minute by minute – to get a good handle of what is going on,” she said. “Then I wrote flash algorithms to mathematically and digitally pull out the things I’m seeing.”

In addition to her poster at AGU, she also gave an oral presentation at the American Meteorological Society conference in Seattle in January. In August, Behnke will present a new poster at the International Commission on Atmospheric Electricity conference in Rio de Janeiro. That poster will compare the volcanic lightning activity at Redoubt to her findings from Iceland.

Her co-authors on the AGU poster are Tech professors Dr. Bill Rison, Dr. Paul Krehbiel and Dr. Ron Thomas, Tech graduate student Harald Edens and Steve McNutt of the Alaska Volcano Observatory.

Lightning Mapping Array: A Significant Breakthrough In Lightning Studies

New Mexico Tech has pioneered lightning research since the 1950s. The Irving Langmuir Lightning Research Laboratory opened in 1963 atop the Magdalena Ridge overlooking Socorro as the first lightning research facility in the United States.

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Dr. Ron Thomas and Dr. Paul Krehbiel deploy a sensing station of the Lightning Mapping Array in 2008 at Mt. Redoubt in Alaska.
Dr. Bill Rison sets up a sensing station in Chile during the 2009 eruption of the Chaiten Volcano.

New Mexico Tech researchers took a huge step forward in the study of lightning with the creation of the first Lightning Mapping Array in 1995 and 1996. The first breakthrough was the initial sensing device, which was engineered by three professors – Ron Thomas, Bill Rison and Paul Krehbiel – and a handful of electrical engineering and physics students at New Mexico Tech.

The students helped show professors that it was feasible to build the system, Rison said. The team of Krehbiel, Rison and Thomas secured a National Science Foundation grant to build the sensor, then deployed the prototype in Oklahoma in 1998 and in western Kansas as part of the Severe Thunderstorm Electrification and Precipitation Study in 2000.

In addition to audible noise (thunder), lightning also produces radio waves, which travel at a known rate – about one foot per nanosecond. With equipment that captures information every 40 nanoseconds, the sensors are 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 use our sensing stations to locate the lightning and track its path.”

That initial test run produced the most detailed three-dimensional images of lightning to date. Since then, New Mexico Tech has provided lightning sensing systems to NASA, the National Severe Storm Laboratory and White Sands Missile Range. Tech also worked with NASA to deploy an array of sensors for the National Weather Service’s forecasting operation in Sterling, Va.

The sensing equipment has three proprietary systems developed at New Mexico Tech – the circuit boards, the firmware and the data analysis software, Rison said.

“The second significant breakthrough was designing sensors that are more compact,” Krehbiel said. “Just before the Mount Augustine explosion in 2006, we developed a portable station about the size of a lightweight picnic cooler that could be easily and quickly transported.”

The first system weighed more than 200 pounds and had only 2 gibabytes of memory, Rison said.  He and other scientists had to download data from the sensors every two days. The current equipment weighs about 10 pounds and has more than 160 gigabytes of memory – enough to capture data continuously for more than three months.

The development of the portable sensing stations allowed Tech scientists to respond quickly to impending volcanic eruptions. In 2006, the Tech scientists deployed three stations at Mt. St. Augustine in Alaska. In 2008, they deployed three stations at Mt. Redoubt, also in Alaska. In 2009, they deployed four stations at Chaiten Volcano in Chile. In 2010, they deployed six stations at Eyjafjallajokull in 2010.


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By Thomas Guengerich/New Mexico Tech