Solar Flares And Radio Communications — How Precarious Are Our Electronics?

On November 8th, 2020 the Sun exploded. Well, that’s a bit dramatic (it explodes a lot) — but a particularly large sunspot named AR2781 produced a C5-class solar flare which is a medium-sized explosion even for the Sun. Flares range from A, B, C, M, and X with a zero to nine scale in each category (or even higher for giant X flares). So a C5 is just about dead center of the scale. You might not have noticed, but if you lived in Australia or around the Indian Ocean and you were using radio frequencies below 10 MHz, you would have noticed since the flare caused a 20-minute-long radio blackout at those frequencies.

According to NOAA’s Space Weather Prediction Center, the sunspot has the energy to produce M-class flares which are an order of magnitude more powerful. NOAA also has a scale for radio disruptions ranging from R1 (an M1 flare) to R5 (an X20 flare). The sunspot in question is facing Earth for the moment, so any new flares will cause more problems. That led us to ask ourselves: What if there were a major radio disruption?

Sol Versus Ionospheric Propagation

This happens more often than you might think. In October, AR2775 set off two C flares and while plasma from the flare didn’t hit Earth, UV radiation caused a brief radio outage over South America. The X-ray and UV radiation travel at the same speed as light, so by the time we see a flare, it is too late to do anything about it, even if we could.

The effects are mostly related to the propagation of radio waves via the ionosphere. In the 1700s, who would care? In the mid 20th century, though, lots of things relied on this property of high-frequency radio waves. Today, it might not matter nearly as much.

If you own a shortwave radio, you may have noticed there isn’t as much to listen to broadcast-wise as there was decades ago. Broadcasters that want to reach an international audience use the Internet to do that now unless they are targeting a part of the world where Internet is rare or restricted. Even the AM radio band isn’t the mainstay it used to be. Many people listen to FM (which propagates differently), satellite radio, or they stream audio from the Internet. Sure, that uses radio, but not ionosphere propagation.

Intercontinental Transit

Perhaps the biggest commercial users of the radio bands now are transoceanic aviation and ships at sea, but even then, many of those uses are now using satellites and much higher frequencies. Ham radio operators are still there, of course, as are some time and frequency standard stations like WWV. While there were some radio frequency navigation systems like LORAN and Gee, these are nearly all gone in favor of GPS.

Would a disruption of these services be a big deal? Probably not, although if you are on a plane or at sea, you might get a little tense. Then again, it just depends on how important that radio device is to you and how many alternatives you have.

Then again, truly big events — so-called Carrington events — can affect a lot of electronics directly. The insurance industry thinks it could run up to $2.6 trillion in damages. Worried? Maybe keep an eye on the space weather channel. If you are interested in what the United States government would do if we had another Carrington-level event, they have it all written out. Honestly, though, the plan seems to be, in summary, do better forecasts and develop new technology. FEMA has an info-graphic that asserts that a solar flare could affect your toilet, although it seems like it would take quite a while for that to happen. It is a bit more interesting to read their excellent but unreleased memo on the topic. The maps on page 16 and 17 showing where the power grid is vulnerable to geomagnetic storms is particularly interesting.

38 thoughts on “Solar Flares And Radio Communications — How Precarious Are Our Electronics?

  1. I got to wondering recently if dire predictions of EMP events “killing every transistor” are more based in the relative delicacy of 60s germanium, upon which silicon bipolars improved, then upon which FET types and subsequent CMOS tech have reduced the susceptibility to negligible amounts.

    Not saying a “Carrington Event” won’t at least be a rough few weeks, just not convinced it would be “reversion to stone age” like some prognostications have it.

    1. CMEs and their resulting geomagnetic storms don’t kill transistors, or really anything that doesn’t have a hundred-mile-long antenna. People often conflate nuclear EMP effects (which includes a strong radiofrequency component that can damage small, isolated electronics) with geomagnetic storms. The only way your phone would suffer, for example, would be due to power grid failure depriving it of a battery recharge and a network to talk to.

      1. Yes the geomagnetics mostly affect infrastructure. CMEs do have broadband RF blasts, which mostly miss or get deflected, and it’s protons that fry outer satellites. However, sufficiently intense and directly aimed at Earth flares are likely to pry open the magnetosphere enough that old Sol can lovingly lick us with a tongue of strong broad band RF.

        1. The magnetosphere doesn’t stop RF. The ionosphere does at low enough frequencies, but the path from the sun to the ground is quite transparent to everything from upper HF/lower VHF until the millimeter-wave absorption bands.

          There are radio bursts associated with flares, CMEs, and such, but those are many orders of magnitude too weak to damage anything. At most, they can cause temporary interference for radio systems. And they make it to the surface quite unimpeded normally, so there’s no mechanism for a CME impact to make them worse.

          1. Also, bulletproof vests don’t stop bullets, the kevlar or ballistic plate inside them does. The ionosphere is considered to be the lowest part of the magnetosphere. However, if something shoves the ballistic plate out the way, like an accompanying magnetic flux that shoves all the ions to the poles and makes the pretty lights, then the incident bullets hurt more.

          2. It’s *transparent*, but extremely *dispersive*, which is important. For instance, the E1 component of an EMP occurs on nanosecond timescales: the *actual energy* absorbed by the device is extremely small, but because it’s compressed to tiny timescales, the voltage far exceeds breakdown and Bad Things happen.

            A coherent impulse like that can’t get through the ionosphere: it’d get dispersed massively, and the energy would spread out over microseconds – meaning the voltage the electronics sees would be far, far lower. So in some sense the ionosphere *does* protect against RF blasts, although any impulse from the Sun is already highly dispersed by the time it hits the Earth anyway, and things like EMPs are actually caused by impulses generated by insulators induced by gamma ray ionization.

            However, specifically for the Sun, “broadband RF blasts” aren’t a worry. Why? Because we already have a massive, massive “broadband RF blaster” right below our feet. Imagine viewing things just by temperature: the entire Earth is sitting below you, at 300 K, covering half of the world for you. The sky’s at 3K (it’s transparent at RF), and the Sun’s sitting there, a little half-degree circle of 5000K. The Earth covers nearly half a million times more of your view, even though it’s 1/20th as hot.

            Now suppose the entire Sun goes and gets a *half-million* times hotter, and… the total “average temperature” you see goes up by ~20. Imagine you’re watching the noise floor on your spectrum analyzer (and suppose you’ve got enough gain you can see the thermal floor), and… it goes up by 13 dB. Whoop de doo. And that would be a *psychotically* huge flare.

            If you want to see what the “broadband RF” viewed from a very, very big flare looks like, take a look here – and that’s with ~70+ dB of gain.

        2. Don’t forget about the South Atlantic Anomoly wonder how the Starlink sats are navigating it. It’s a bit of a weakspot in our magnetosphere and special precautions are needed when moving through it. Wouldn’t mind seeing the effects myself caused when humans go through it, I imagine its like you own personal laser light show in your eyes! LOL

      2. Back in the 80s I did computer and phone network planning things at Bell Labs. One group that ended up in my department was a bunch of physicists studying EMP effects on the network. Sometime in the ?late 60s? there was a big solar flare that took down a long-haul telephone trunk from Chicago to NY, back when those were made of copper instead of fiber. It was basically an 800-mile-long antenna, and the flare pushed enough current into it that it fried the equipment at the ends. Electronic switching systems aren’t thrilled with the voltage, but even the earlier electromechanical ones could get themselves spot-welded. (Fortunately, with fiber, this problem is mostly gone.)

    2. “Not saying a “Carrington Event” won’t at least be a rough few weeks, just not convinced it would be “reversion to stone age” like some prognostications have it.”

      The event on its own won’t cause stone age. Even if every transistor (on the surface) would die. There is enough base technology around to restart from a advanced level to get back into production soon. And there should survive quite some, that are protected somehow.

      But sociodynamics could very well turn all very sour. Panic can go viral, too. There is a saying that every civilisation is 2 meals away from breakdown.
      Have the carrington event kill the internet and major traffic and communication – and you will probably have empty supermarkets (btw. how to pay there, before they are empty?) soon and looting and shooting for the leftovers.

      People acted already pretty wild, for the hunt for toilet papers.

    3. From memory of discussions with my dad (power system protection engineer), the big risk from a Carrington scale event in this age is that the transformer cores pick up a large magnetic polarisation due to the DC current. They would need about 2-3 days to naturally demagnetize. Modern power grids (and their protection systems) are able to handle almost every other aspect of a CME.

      1. Not buying that. Sure, transformers will saturate and cause breakers to trip, but nothing worse. Transformers operate fairly close to saturation, so I would need to see evidence that it takes more than a second to fully degauss them, just by applying normal AC power.

        1. You’re not far off, but I think you underestimate the potential issues of residual magnetization in a transformer. When inrush currents can spike high enough to deform windings and cause other damage to a transformer, failures can cascade and take out the transformer. Small low voltage transformers might be too small for this to happen. But I think a medium to low voltage voltage step down transformer in your neighborhood or especially a high voltage transformer for major grid ties could be damaged this way.

          A good article explaining why de-magnetization is important:

          1. I didn’t read the whole article, since that’s about how to demagnetize, which is pretty simple. The important thing here, is that a transformer left in a magnetized state CAN have an initial surge of about twice the normal full load, and this only happens for a few cycles, that is, around a TENTH of a second. Any transformer that suffers from deformed windings due to this kind of overload is a very poorly designed transformer, since this has been a KNOWN PHENOMENON for decades. Not just from things like solar flares, but from the simple fact that if a transformer is deenergized at some random point in the waveform rather than at a zero crossing in the current, it retains the flux that was present at the moment it was deenergized. So while the article prescribes a procedure for demagnetizing transformers, the fact is that all transformer engineers are aware of this, and design to tolerate it.

            This is a whole lot of hand-wringing for nothing.

          2. Ok you may be right about whether a transformer would actually be damaged this way. But it could definitely blow fuses and trip breakers. According to it can be equal to short circuit fault levels. Many of the substation breakers would hopefully have automatic reclosers or at least be closed remotely. But the transformers on a pad or a pole in your neighborhood are probably fused, and fuses take work to replace. So I’m just not sure you’d want to roll the dice and just turn everything back on and hope everything still works.

          3. @Grey Pilgrim: Having a transformer blow a fuse/breaker is a normal phenomenon. I have a VARIAC (1,8kW toroid core) for which I had to build an inrush current limiter. Otherwise I had a 50% chance for a tripped breaker when I plugged it in.
            I do not know, how the big utility transformers are connected to avoid this. Perhaps only very slow blow fuses which would not be a problem, as a transformer has a huge thermal mass.

      2. I remember the ’89 event, I was watching someone and I think she fell asleep before the power was off. I couldn’t leave because she was five, and her mother came late, deciding to drive people home. I did worry about getting home in the dark, no traffic or street lights. But I’m sure power was restored before I went to bed, so maybe it was off for about five or six hours.

        So it tripped something, but it was too fast to get a replacement and replace a transformer.

        They said at t theye time that it was the long runs of cables from the hydro generators up north, acting as antennas. So the delay was likely getting people to where the problem was.I

        I’ve lived through longer power outages.

        1. I’d imagine there’s utilities down south, with stocks of some spares and the experience of putting things right ASAP after hurricanes, and ditto up north for ice storms and extreme blizzards, and a stripe across the middle that will have to wait until the Northerners and Southerners have got their own crap under control and come to help out.

          1. Respectfully, while I have seen many weaves of false dichotomies, I haven’t seen a weave as yours. Wheret is that middle, you speak of, is that middle that has it’s share a natural disasters? Why do you believe they aren’t as prepared as other are? I suppose there will be always be those who have to manufacture something, to be able to kick down.

      3. They don’t have to pass the DC current for very long … sure it can jump a morse code key, but I doubt it can jump the mechanical relays used for the HV grid. Or build in massive DC generators/blockers which can offset the imposed power, so you don’t have to shut down.

        Or use HVDC, which simply doesn’t give a damn … it’s just a little extra or a little less load.

  2. From the FEMA memo – Further, the March 13, 1989 storm that collapsed the Hydro Quebec power grid in
    Canada came within seconds of collapsing the Northeast and northern Midwest U.S. power grid
    (Kappenman, 2005). Kappenman (2005) reports that “the size and intensity of this Westward
    Electrojet structure, had it developed 5- 7 h later, would have extended from east coast to west
    coast of the entire northern-latitude portions of the US power grid, and is likely to have produced
    much more significant consequential impacts … . ” It should be noted that the power grid, due to
    deregulation since 1989, is actually more vulnerable today (National Academy of Sciences,

    This stuff is a very real risk. A lot of the big transformers for the USA power grid are no longer made in the USA and there are few if any spares. Lead time can be months or even years. Civilization is a very thin veneer on a big ball of rock. One little storm or a virus can cause havoc. Not much point in worrying since there isn’t a lot you can do. Just hope it doesn’t happen and maybe keep a couple spare rolls of toilet paper.

    1. At least we have better early warning than we did then. STEREO, ACE, and DSCOVR let us see a CME coming with, in theory, enough time to SHUT DOWN EVERYTHING and save the transformers. But in practice, that would require somebody with the authority and confidence to create a large, voluntary blackout on a few minutes’ notice. Good luck finding that in the bureaucracies.

      1. Actually, You’ll have to disconnect devices from the powerlines to avoid damage. Considering the US still has an absurd amount of manual-switched gear, that’s not going to happen in time.

        Yes, you may prevent it from cascading towards those areas with up-to-date infrastructure. But realistically…

        1. You’d have to disconnect substations from the power lines leading from them to protect the transformers. If that isn’t done substation transformers would fry and according to a documentary I saw on this it could take months to a year to restore power because of the very limited production capacity of them. I don’t know if the documentary took into consideration a crash program to create emergency production capacity. Anyway, even “just” months for restoration would produce a degree of this:

          James Burke Connections, Ep. 1 “The Trigger Effect”

      2. Save the transformers???? Transformers are made of silicon iron laminations and copper wire. In large transformers it’s not even insulated wire; wires are physically separated and insulated by either mineral oil or SF6 gas. So please explain to me what part of a transformer gets damaged. The bulk of damage from transient events is fuses, and outages like the one described are for the most part limited to the time it takes to get people out to the blown fuses to replace them.

          1. From appendix C:
            “If transformer half-cycle saturation is allowed to continue, stray flux can enter the transformer structural tank member and current windings. Localized hot spots can develop quickly inside the transformer’s tank as temperatures rise hundreds of degrees within a few minutes…”

            In what world are power transmission networks allowed to run for MINUTES under severe overload conditions? Two words here: CIRCUIT BREAKER. Seriously, if our power system can’t deal with this without equipment damage, it’s a miracle it works from day to day. I’m not saying that flares and CMEs shouldn’t cause power outages. I’m saying it should not cause equipment damage.

          2. One possible concern is that breakers and fuses that are designed for an AC overload may not be effective for a DC overload. An AC arc is interrupted 120 times a second and may be quenched when interrupted. A DC arc is continuous and won’t be so easily quenched.
            Looking at the problem optimistically, the transformer doesn’t disappear just because part of it has melted. It may be possible to rebuild or repair it far more quickly than ordering new.

          3. Chris Maple: Here’s the thing: you can’t induce a DC current in a wire. To do so would require a continuously increasing magnetic field, and you can only sustain that for a little while. Because Faraday’s law. There IS no extended DC current, even from a solar flare. There CAN be AC current that’s too low in frequency for the transformer’s design. So there may be some arc-over in the breakers because they can’t really wait around too long for a zero crossing, but it’s not going to be DC.

            The problem wish a solar flare is not that it induces a DC current in the transmission line, but that there can be an intense magnetic field that IS continuous, at least for a while, which can saturate transfomers, causing them to act like shorts. But guess what? The current you need to break in that case is 50 or 60 Hz AC, so no problem.

  3. As a ham radio operator, I welcome the sunspots and hope for many more. Radio blackouts aren’t any fun but an the last 2 solar cycles have sucked with low sunspot numbers. I’ve been a ham for 25 years and occasionally I hear the older hams talking about how easy it was to make worldwide contacts on 10 meters, a band that’s been dead for most of the time I’ve been licensed.

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