On November 8, 2020, the sun exploded. Well, it’s a bit dramatic (it explodes a lot) – but a particularly large sunspot named AR2781 produced a C5-class solar flare that is a medium-sized explosion even for the sun. Flares range from A, B, C, M and X with a scale from zero to nine in each category (or even higher for giant X flares). So a C5 is about dead center of the scale. You may not have noticed it, but if you lived in Australia or around the Indian Ocean and used radio frequencies below 10 MHz, you would have noticed it since the flare caused 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 scale for radio interference from R1
This happens more often than you might think. In October, AR2775 released two C-flares, and while plasma from the flare did not hit the ground, UV radiation caused a brief radio break across South America. X-rays and UV radiation move at the same speed as light, so when we see a flare, it is too late to do anything about it, even if we could.
The effects are mainly related to the propagation of radio waves via the ionosphere. In the 18th century, who cares? But by the middle of the 20th century, many people relied on this property of high-frequency radio waves. Today, that may not mean much.
If you own a shortwave radio, you may have noticed that there is not as much listening to broadcasting as there was decades ago. Broadcasters who want to reach an international audience use the Internet to do so now, unless they are targeting a part of the world where the Internet is rare or limited. Even the AM radio band is not the mainstay it used to be. Many people listen to FM (which propagates differently), satellite radio, or they stream audio from the Internet. Sure, it uses radio, but not ionosphere propagation.
Perhaps the largest commercial users of radio bands now are transoceanic aviation and ships at sea, but even then many of these uses now use satellites and much higher frequencies. Ham radio operators are still there, of course, as there are some standard time and frequency stations like WWV. While there were some radio frequency navigation systems like LORAN and Gee, these are almost all gone in favor of GPS.
Would a disruption of these services be a big deal? Probably not, even if you’re on a plane or at sea, you can get a little tense. So it just depends on how important that radio device is to you and how many options you have.
Then again, really big events – so-called Carrington events – can affect a lot of electronics directly. The insurance industry believes it could run up to $ 2.6 trillion in compensation. Worried? Maybe keep an eye on the space weather channel. If you’re interested in what the US government would do if we had another Carrington – level event, they’ve all printed it out. Honestly, however, the plan seems to be, summarize, make better forecasts and develop new technology. FEMA has an infographic that claims that a solar flare can affect your toilet, even though it seems like it will take quite a long time before it happens. It’s a little more interesting to read their excellent but unpublished note on the subject. The maps on pages 16 and 17 which show where the power grid is vulnerable to geomagnetic storms are particularly interesting.