On November 8, 2020, the sun exploded. Well, that’s a bit dramatic (it explodes a lot) – but a particularly large sunspot called AR2781 produced a C5-class solar flare that’s a medium blast even to the sun. Torches range from A, B, C, M and X with a scale from zero to nine in each category (or even higher for giant X torches). So a C5 is roughly in the middle of the scale. You may not have noticed, but if you lived in Australia or around the Indian Ocean and used radio frequencies below 10 MHz, you would have noticed since the torch triggered a 20-minute radio blackout on those frequencies.
According to NOAA’s Space Weather Prediction Center, the sunspot has the energy to produce M-class flares that are an order of magnitude more powerful. NOAA also has a radio disturbance scale ranging from R1 (an M1 flare) to R5 (an X20 flare). The sunspot in question is currently facing Earth, so new flares will cause more problems. That led us to wonder: What if there was a major radio interference?
This happens more often than you may think. In October, AR2775 caused two C flares, and although plasma from the flare did not hit Earth, UV radiation caused a brief radio blackout over South America. The X-ray and UV rays travel at the same speed as light, so by the time we see an eruption, it’s too late to do anything about it, even if we could.
The effects are usually related to the propagation of radio waves through the ionosphere. Who would care in the 18th century? However, in the mid-20th century, many things relied on this property of high-frequency radio waves. Nowadays it may not matter nearly as much.
If you have a shortwave radio, you may have noticed that there aren’t as many broadcasts to listen to as there were decades ago. Broadcasters looking to reach an international audience are using the internet to do so now unless they target an area of the world where the internet is rare or limited. Even the AM radio isn’t the mainstay it used to be. Many people listen to FM (which spreads differently), satellite radio, or stream audio from the Internet. Sure, that uses radio, but not ionosphere propagation.
Intercontinental transit
Perhaps the biggest commercial users of the radio bands are now transoceanic aviation and ships at sea, but even then many of those applications now use satellites and much higher frequencies. Ham radio operators are still around, of course, as are some time and frequency standard broadcasters like WWV. While there have been some radio frequency navigation systems like LORAN and Gee, almost all have gone in favor of GPS.
But then again, really big events – so-called Carrington events – can directly affect a lot of electronics. The insurance industry thinks it could take up to $ 2.6 trillion in damage. Worried? Maybe keep an eye on the space weather channel. If you’re interested in what the United States government would do if we had another Carrington level event, they wrote it all down. In all fairness, the plan, in summary, appears to be making better predictions and developing new technology. FEMA has an info graphic claiming that a solar flare can affect your toilet, although it seems like it will take a while for that to happen. It’s a bit more interesting to read their excellent but unreleased memo on the topic. The maps on pages 16 and 17, which show where the electricity grid is vulnerable to geomagnetic storms, are particularly interesting.