Solar flares can send powerful radiation and energetic particles toward Earth, disrupting communications. Typically, these events are monitored and forecast with satellite observations and networks of specially designed instruments, but detailed studies could also get a boost from amateur radio operators on Earth, report Frissell et al.
Amateur radio, popularly known as ham radio, uses frequency bands in the radio spectrum that are set aside for noncommercial use. Particularly in the 1.8- to 30-megahertz bands, the geographic range of ham communication depends on the conditions of the ionosphere—the layer of the atmosphere, roughly 85 to 600 kilometers high, that is ionized by the Sun’s radiation. The layers within the ionosphere can reflect signals back to Earth, allowing operators to communicate, often with Morse code, across continents and oceans. These communications may be disrupted by significant space weather events, such as blasts of radiation from solar flares suddenly impacting Earth’s upper atmosphere.
In recent years, ham operators have established global networks of radio stations to monitor ionospheric conditions in real time, sometimes using automated equipment and software that allows for continuous monitoring across multiple bands. This makes these networks potentially helpful to scientists who study space weather.
To demonstrate, the authors compare data from one such network, the Reverse Beacon Network (RBN), with observations from the U.S. National Oceanic and Atmospheric Administration’s Geostationary Operational Environmental Satellite-15 (GOES-15) during a powerful solar flare on 13 May 2013. Just before GOES-15 observed the flare’s peak, RBN had thousands of links between stations in its network, including more than 1100 links operating on high-frequency bands from 7 to 28 megahertz across Europe, North America, South America, and Africa.
Immediately after the peak, more than 65% of all radio links on RBN dropped out, and nearly all communication on the 7- and 28-megahertz bands was lost. South America and Africa were completely cut off, and most links between the United States and Europe fell silent. Thirty minutes after the flare’s peak, conditions began to improve, and some transatlantic communication was restored, as well as some links to the Southern Hemisphere.
This event demonstrates both the global spatial coverage and diverse frequency space observed by just one amateur radio network. Amateur radio data sets have great potential for validating space weather models and understanding how the ionosphere behaves on a variety of spatial and temporal scales. The real-time nature of these networks also makes them useful for space weather nowcasting.
Because ham radio equipment is, by nature, not standardized and is run by enthusiasts who operate in their free time and can afford to purchase it, there are geographical biases in the data. However, by incorporating the ham networks with other data sources—and perhaps encouraging greater standardization, in the future, by participating ham radio operators—the authors think the data will prove a valuable addition to space weather science. (Space Weather, doi:10.1002/2014SW001132, 2014)
—Mark Zastrow, Freelance Writer
Citation: Zastrow, M. (2015), Radio blackout! Ham radio as an operational and scientific instrument, Eos, 96, doi:10.1029/2015EO024075. Published on 16 February 2015.