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No one has a firm grasp on the dimensions and activity of the lowest part of our upper atmosphere, known as the ionospheric D region, because it's literally a moving target. Located 40 to 60 miles above the Earth's surface, the region moves up and down, depending on the time of day. And it's nearly impossible to monitor: it's too high for airplanes and research balloons, too low for satellites, and not dense enough for direct radio sounding.
Understanding the D region does more than benefit scientific research. It can also affect a wide range of military technologies, including improving the accuracy and resolution of low-frequency navigation systems. Such systems can be alternatives to GPS and are of growing importance to the military.
Solution - Researchers - Storms - Waves - Researchers
The solution, researchers discovered, is lightning storms. By measuring the electromagnetic waves produced by lightning, researchers were able to retrace the lightning's path to diagnose the electron density of the region.
Co-authored by engineering students Sandeep Sarker (MS '17) and Chad Renick (BS '17, MS '18, current Ph.D. candidate), the study was published in December in Geophysical Research Letters. The study was supported by grants from the National Science Foundation and the National Science Centre, Poland.
Storm - Flash - Sends - Range - Frequencies
During a storm, a flash of lightning sends out a wide range of electromagnetic frequencies. The speed of those waves changes based on the conditions of the upper atmosphere. Previous theoretical research measured the electromagnetic waves to gauge the lightning's origin.
"I kind of reversed the problem," says study author Mark Golkowski, Ph.D., associate professor of electrical engineering and bioengineering in the College of Engineering, Design and Computing. "If I knew where lightning was coming from, then I could accurately diagnose the upper atmosphere along the path that it traveled."
Golkowski - Lightning - Group - Velocity - Speed
Golkowski measured the lightning's group velocity – the speed at which the energy of a wave travels....
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