CONWAY, Ark. (November 10, 2016) – This fall, the
Journal of Applied Physics
published
“Detection of Atmospheric Infrasound with a Ring Laser Interferometer,”a paper by Hendrix physics professor Dr. Robert Dunn.
The peer-reviewed paper is the culmination of a four-year National Science Foundation Research in Undergraduate Institutions (NSF RUI) grant-funded project using the College’s ring laser interferometer, which can detect and analyze atmospheric infrasound sound
waves with frequencies below the lower limit of human hearing and acoustic-gravity waves.
The study includes ring laser data from a 2014 EF4 tornado that struck central Arkansas to demonstrate the ring laser's potential to supplement Doppler radar and satellites, particularly in areas of limited radar and satellite coverage, and serve as an early-warning
system for natural disasters.
"We essentially verified many of the results from a long-term study by the U.S. National Oceanic and Atmospheric Administration (NOAA) but we substituted a ring laser in place of microphones," said Dunn.
The group's ring laser was able to "clearly show the frequency spectrum of the infrasound," he said.
Hendrix researchers detected infrasound from tornadoes 30 minutes before the tornado funnel was on the ground.
"The detection of infrasound 30 minutes before a tornado is on the ground, in conjunction with Doppler radar, could prove very useful as an early warning system," Dunn explained. "And the ability to detect the rotational components of earthquake-generated seismic waves may help reduce the damage
from earthquakes … because building codes often neglect the effects of ground rotation."
Beyond tornado early warning systems, ring lasers can also detect infrasound from hurricanes and volcanoes.
"Volcanic ash can destroy jet engines, so the ability of an array of ring lasers to detect volcanic eruptions in remote locations like the Aleutian Islands could help to ensure the safety of commercial aircraft that regularly fly over the region," he added.
Dunn was assisted by Hendrix student Angela Lamb ’17 and former student researchers Elijah Kessler ’16 (now an engineering student at Washington University) and John Meredith ’11 (now with the Center for Earthquake Research and Information at the University of Memphis).
Shortly after the paper’s publication, science publications such as
Science World Report and
Phys.Org picked up on the ring laser’s potential for early detection of natural disasters.
Dunn was apprehensive about the early attention.
“Ring lasers haven’t lived up to scientists’ expectations. They’ve been overestimated, and I don’t want to continue that,” said Dunn, who joined the Hendrix Department of Physics in 1988 after retiring from the United States Air Force. His early teaching and research at Hendrix were initially underwritten by a Research
Corporation grant.
Interferometers were introduced in 1881 by Albert Michelson, who in 1907 became the first American to receive a Nobel Prize in the sciences. In February 2016, the Laser Interferometer Gravitational Observatory (LIGO) announced the detection of gravity waves from two colliding black holes. The LIGO design
incorporated aspects of the Michelson Interferometer.
By 1963, ring laser interferometers were developed that could measure rotation. Shortly after this discovery, the aerospace industry launched a major effort to replace mechanical gyroscopes in aircraft and missiles with small navigational ring laser
gyroscopes.
More recently, large ring laser interferometers such as the one at Hendrix used in Dunn’s research have been designed to measure geophysical effects.
This fall’s publication is Dunn’s fifth published paper on the topic, which include ring laser interferometer readings from a typhoon in the Philippines, a volcanic eruption in eastern Russia, and four Gulf hurricanes. The ring laser has also been used to observe activity related to natural gas fracking in northern
Faulkner County, Dunn said.
At this point, all of their results "must be considered preliminary," and the group's goal is to "continue exploring how ring lasers can help reduce the impact of natural hazards," Dunn stressed.
All of the research was conducted on campus during the summer with Hendrix students.
In addition to NSF funding, Dunn’s research has been supported by the NASA Space Grant Consortium, as well as the Hendrix Odyssey Program.
“Our number one goal is teaching. “For science, that teaching would be helped by doing research to reinforce what we do in the classroom,” said Dunn, adding that the College’s record of getting research students into graduate science programs is “quite
impressive.”
About Hendrix College
Hendrix College is a private liberal arts college in Conway, Arkansas. Founded in 1876 and affiliated with the United Methodist Church since 1884, Hendrix is featured in Colleges That
Change Lives: 40 Schools That Will Change the Way You Think about Colleges and is nationally recognized in numerous college guides, lists, and rankings for academic quality, community, innovation, and value. For more information, visit
www.hendrix.edu.