A new study by Geophysical Institute researchers links lightning activity to volcanic eruptions.

Since the 1960's, intense lightning displays have been recorded accompanying many large-scale volcanic eruptions. For the first time, scientists were able to collect data fully describing lightning activity during the 2006 Mt. Augustine eruption, according to an article published in the journal Science last week.

"It was a combination of being at the right place, at the time, with the right instruments," said Steve McNutt, a co-author of the study and a volcanologist at the GI.

The article discusses the levels of electrical activity, lightning, corresponding to several eruptions of various magnitudes.

During the initial Augustine eruptions in 2006, airline pilots reported lightning in the ash plume. This prompted McNutt to install new lightning detection instruments developed by the Lightning Research Group at the New Mexico Institute of Technology. Two instruments capable of detecting the exact location and source of each lightning bolt were installed on the coast of Cook Inlet, days before a series of eruptions.

"We were very lucky," McNutt said. "Eruptions of this magnitude only occur a couple times each year. We were able to put our instruments out there in time to get a lot of good data."

McNutt became interested in lightning shortly after coming to the GI, when he noticed lightning was affecting the seismic data for Mount Spurr in 1992. Working in collaboration with scientists from MIT, McNutt continued to look at the connection between lightning and volcanic eruptions.

It is a correlation that Homer residents have also noticed, McNutt said.

"I have gotten a couple of calls from local residents who called to say they had seen lightning and wanted to know if Mount Augustine was erupting," he said.

Lightning is a rare occurrence along the Aleutians. Cold air surface temperatures cannot hold enough water vapor to form the large cumulous clouds that produce lightning.

Lightning is the release of built up electrical energy in cumulous thunderclouds. As convection causes cumulus clouds to grow, particles in the upper levels freeze, separating positive and negative charges.

Circulating air within the cloud further separates the charged particles, establishing a negatively charged base and a positively charged top. Lightning results from the build-up and discharge of electrical energy between positively and negatively charged areas of the storm, and between charged portions of the storm and the ground.

Volcanic ash clouds are similar to thunder clouds, explaining why lightning is often seen during large eruptions. In volcanic ash clouds, an electric charge is generated from the friction of ash particles expelled into the air, particle collisions and rock fractures.

Ash clouds from large eruptions are composed of particles of various sizes. Larger particles tend to be negatively charged and fall to the base of the cloud while smaller positively charged particles remain near the top, re-creating the same electric distribution seen in thunderclouds. As charges and particles build up energy is released in the form of lightning.

Lightning is the primary cause of forest fires in interior Alaska and is monitored by the Alaska Fire Service under the federal Bureau of Land Management. Less than 20 small antennas monitor cloud-to-ground lightning across the state. The National Weather Service, National Oceanic and Atmospheric Administration and BLM use this data in aviation forecasts, fire watches and general weather postings.

Tom Dang, a meteorologist with the National Weather Service in Anchorage, said lightning strike data is important to verify weather conditions.

"Lightning reports and data are important for our forecasts," he said. "We don't have radar systems for the entire state and the lighting reports confirm what is happening weather-wise in remote areas."

McNutt is also trying to use lightning data as an indicator of volcanic activity.

"In poor weather conditions and at night, when wind and rain pound the ground disturbing our seismic instruments, we can look at lightning data and try to understand what's going on with the volcano, and the ash clouds," he said.

The published article just scrapes the surface of data collected from the 2006 Mount Augustine eruptions, McNutt said. He plans to continue working with the data to further define the relationship between electrical activity and volcanic ash cloud composition.

Other UAF researchers involved in the article were Guy Tytgat and Edward Clark, who contributed technical support.