Lightning is one of nature’s most fascinating phenomena. In less than a millisecond, a kilometers-long plasma channel sinks an unimaginable electrical current from a cloud to the ground, unleashing vast amounts of energy in a very short period of time. Nearby observers will see a brilliant flash of light and hear (and feel!) a shockwave of thunder from the superheating of the air surrounding the bolt. However, did you know that the effects of lightning are also detectable as radio signals across thousands of kilometers?
A group of researchers led by Prof. Dr. Egon Wanke of Düsseldorf, Germany, started the Blitzortung project a few years ago. Blitzortung is a worldwide, non-commercial, crowd-sourced Time-of-Arrival (TOA) lightning detection and location network. Around the world, hundreds of stations listen for the tell-tale electromagnetic signature of a lightning stroke in the VLF range (roughly 3 to 30 kHz). When a stroke is detected, each station records the characteristics of the signal and a precise GPS timestamp, and then transmits this information to a central server.
When a probable lightning stroke is detected by multiple stations, the server uses the timestamps and the speed of light to locate the lightning strike. If station A detected the stroke at time tA, and station B detected the stroke at time tB, then the lightning stroke had to occur somewhere along a hyperbolic curve, as a time difference of 100 microseconds corresponds to a distance difference of 30 kilometers. Compute curves for at least three pairs of stations and they will hopefully all meet at exactly one point. This is the essence of Time-of-Arrival location finding.
Prior to this summer, the nearest station was about 400 km from Rochester, outside of Philadelphia. This station was still able to detect a significant number of lightning strokes from Rochester and beyond! That’s because lightning produces an extremely strong, extremely low-frequency electromagnetic pulse which bounces between the ground and the ionosphere for thousands of kilometers, like an atmospheric waveguide. However, two Rochester-area stations went live in late summer, providing additional coverage for storms in the Northeastern US.
One of those stations is in Interlock Rochester’s space in the Hungerford building. It consists of a custom-built magnetic loop antenna, a Blitzortung amplifier board, and a Blitzortung controller board. As of this writing, it has been active for two weeks and has detected 30,282 lightning strokes, the longest of which was 4,350 km away! This is despite our antenna being located inside of an industrial building on the outskirts of downtown.
(Props to W2NED and the rest of the crew who built the other station, located in Naples, New York.)
Total costs were approximately:
- Blitzortung PCB and parts (amplifier, controller): €120
- Antenna parts from Lowes: $20 (??)
- STM32F4DISCOVERY ARM board from Mouser: $15
Future improvements include 3D-printing an enclosure for the amplifier (and perhaps the controller) and finding a better location to hang the antenna. While we’re approaching the winter months and won’t see much lightning until the spring, we’ve still got thundersnow to look forward to!
For more information on the Blitzortung project, visit their web site at blitzortung.org. You can see statistics for our station at the Lightning Maps site. Also, you can see the real-time map of lightning strikes at http://www.lightningmaps.org/realtime!