Thousands Of Amateur Radio Operators Measured The Solar Eclipse's Effects On The Atmosphere

Astronomers and space fans may have set up lawn chairs outside to watch the eclipse, but Nathaniel Frissell set up his ham radio. As the sky dimmed and daylight turned into an uncanny dusk, the reports started coming in: Communication was dying off over the 20m (14 MHz) radio band.

The 2017 solar eclipse.Photo: Bernd Thaller (Flickr)

Frissell (call sign W2NAF) was one of thousands of hams who set up their radios on the day of the solar eclipse in an effort to measure its effects on the upper atmosphere. They have just release the results of their investigation, which found that the solar eclipse thinned the charged particle-containing part of the upper atmosphere, called the ionosphere.

"It's been a really amazing thing to see the entire ham radio community come together and see this through," said Frissell, a professor at the New Jersey Institute of Technology Center for Solar-Terrestrial Research who organised the event. "We have been able to take this really rough piece of physics and science data that wasn't designed for this in the first place and show the eclipse effects in a very clear manner."

Amateur, or ham, radio operators are folks who set up radio communications and send messages to one another as a hobby. They communicate over specially designated FCC radio bands. Occasionally, organisations will host "QSO parties," where hams try and establish contact with as many other radio operators as they can.

Ham radio operators bounce signals off of the ionosphere to send messages over long distances, so they're interested in how space weather, like solar flares, or eclipses change how their messages travel. HamSCI, a group that promotes and performs citizen science research by amateur radio operators, organised a QSO party during the eclipse. The HamSCI researchers monitored the contacts the hams made through a number of communications observation networks.

Observations of ham radio contacts during the eclipse.Graphic: Frissell et al (GRL 2018)

In doing so, HamSCI created one of the largest datasets ever produced by a citizen science ham radio experiment, according to the paper published recently in Geophysical Research Letters. There were over 30,000 contacts made during the QSO party, said Frissell.

The data revealed the eclipse thinning the ionosphere. Contacts couldn't successfully be made over the long-distance 14MHz, or "20 meter" band during the hour before and after totality — messages went straight into space rather than bouncing back to Earth.

Other bands saw an increase in the distance over which contacts could be made; a layer of the ionosphere that is stronger during the day than at night seemed to have weakened during the eclipse, so it didn't absorb signals as it normally would have. This allowed some signals to travel further before bouncing back to Earth.

The measurements confirmed previous studies; we've previously reported on other experiments that found the solar eclipse created a "wake" in the ionosphere. Others have measured eclipses' effects on ham radio, but this is the largest citizen science experiment to do so.

There's more to learn from eclipses, and perhaps more to pull out of this very data set, said Frissell. And there's even more science to be done — HamSCI is hoping to research how solar flares impact the ionosphere, and aims to build personal space weather stations.

But all-in-all, it's been rewarding. "It was fantastic," said Frissell.

[Geophysical Research Letters]

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