An imperceptible antenna in eastern Colorado, recently installed by University of Colorado Denver engineering researchers, is already making some data-rich noise in the global scientific community.
Buried in a patch of Lincoln County grassland, the extremely low frequency (ELF) receiver is gathering data that has significant implications on research into the upper atmosphere and even into the gravitational waves produced by colliding black holes – a recent discovery that made worldwide news.
Mark Golkowski, PhD, associate professor of electrical engineering at CU Denver’s College of Engineering and Applied Science, and several CU Denver engineering students, along with two colleagues from Poland, installed the receiver in the Hugo Wildlife Area in spring 2015. Hugo Station joins two other remote stations – Hylaty Station (Poland, built in 2005) and Patagonia Station (Argentina, installed in May 2016) – in forming the Polish Worldwide ELF Radiolocation Array (WERA).
Receiving devices at the stations continually measure waves of extremely low frequencies (0.03-300 Hz). “We’re using this data to be able to more effectively model how electromagnetic waves propagate in the Earth-ionosphere waveguide,” Golkowski said. The waveguide is formed by the conductive surface of the Earth and the lower ionosphere. “Lightning around the globe is both a source of perturbation for the ionosphere and a diagnostic of the ionosphere’s current state,” Golkowski said. “There are around 50 lightning strikes around the world per second, and the strikes we detect (at the ELF stations) are typically the most powerful ones.”
Besides providing insight into the effects of lightning, the receivers’ data can also be used in other atmospheric inquiries, including research into solar X-ray bursts and various electrical phenomena.
The worldwide network is a collaboration between two American partner institutions – CU Denver and the Massachusetts Institute of Technology – and Jagiellonian University in Poland. Jagiellonian University provided the hardware for Hugo Station.
Insight for gravity wave research
In an exciting yet unexpected development, data from these stations is now also being used as part of gravity wave research. In September 2015, researchers at the Laser Interferometer Gravitational Wave Observatory (LIGO) discovered gravitational waves that had traveled through the universe for more than a billion years before reaching Earth. The waves were produced by a mammoth event – the merging of two black holes. LIGO acts as a “cosmic microphone” that uses detectors in two U.S. locations (Louisiana and Washington) and another in Italy to pick up ripples in space-time.
Gravitational waves were first predicted by Albert Einstein in his theory of relativity 100 years ago. The waves are a distortion of space-time, Einstein theorized, and LIGO’s discovery of them essentially opens a new window into the universe.
Lightning, however, interferes with LIGO’s detectors, according to Golkowski. “Their system tries to detect extremely small changes in space-time through special sensors,” he said. “Strong electromagnetic impulses from lightning can cause small movements in their sensors – it can create a false positive of a gravity wave when it’s actually an electromagnetic wave.”
To help gravity wave researchers fully understand this type of interference, Golkowski and several other international researchers co-authored a paper that’s currently under review: “Subtraction of correlated noise in global networks of gravitational-wave interferometers.” Data from the Worldwide ELF Radiolocation Array is being sent to LIGO in the United States and Italy.
Finding the perfect off-grid spot
Golkowski and electrical engineering students are also involved with an electronic receiver on Kodiak Island, Alaska, funded by the National Science Foundation, which monitors space weather. Space weather is a leading cause of damage to satellites.
Similar to the Alaska installation, the Hugo station needed to be off the grid and free of interference from power lines. In fact, the requirements for the Hugo station were even more stringent due to the lower frequencies being observed. Although Golkowski initially sought a location in the Rocky Mountains, the eastern part of the state provided much more favorable conditions. Tom Rupert, an Xcel Energy employee and undergraduate CU Denver student at the time, provided information about eastern Colorado power line locations that led to Hugo Wildlife Area being chosen as an ideal station site.
Two current electrical engineering students at CU Denver – Ryan Gillespie and Sandeep Sarker – will use data from the Hugo ELF receiver as part of their MS theses. It is the multi-scale aspects of this research that Golkowski sees as most alluring both for himself and the students.
“From precision micro-electronics to cosmic-scale events, and from working in the field with a pick and shovel to completing sophisticated theoretical analysis on the computer, we offer a broad range of diverse and challenging opportunities,” he said.