We now go live to Ollie Williams for the weather. What’s the weather looking like today, Ollie?
So, this is only tangentially connected to nuclear power, but space weather is a thing and can impact the power grid. Earlier today, the earth was hit by a coronal mass ejection (CME) associated with an X class solar flare. This was a little more severe than projected, causing a G4 class geomagnetic storm. The sun is approaching the solar maximum for this solar cycle, so more flares & CMEs like this are possible over the next few years.
That last paragraph probably didn’t mean much to you if you don’t follow the Space Weather Prediction Center (SWPC). The SWPC is a part of NOAA. It monitors the sun for activity like the flare and issues warnings to anyone who cares, including power companies, if the activity is expected to hit earth. There are a lot of cool satellite images you can look at on their page, in addition to lots of information on how space weather can impact the planet.
Solar flares are bursts of radiation associated with fluctuations in the sun’s magnetic field. The sun’s magnetic field isn’t nice and orderly like ours. It’s a tangled, twisted mess. Sometimes that twisting gets too severe and causes a flare as the lines of magnetic flux reorient themselves.
CMEs are expulsions of millions, or even billions, of tons of highly magnetized plasma from the outer layer of the sun’s atmosphere, the corona. This is usually associated with a solar flare.
Solar flares are ranked according to the intensity of the x-rays released. The classes are A, B, C, M, X. Each is 10x stronger than the previous one, so an X-class flare is 10000 times more energetic than an A-class flare. X is the final letter, but flares more powerful than an X are observed. These are designated by a multiplier, such as X17, denoting that that flare was 17 times as energetic as an X-class.
Solar flares impact earth, often resulting in a radiation storm that limits radio communications. CMEs hitting earth are another matter entirely. The plasm ejected from the sun interacts with the earths magnetic field, twisting and warping it. This warping is what you see in pictures of the aurora. Electrons cascade down the magnetic field and interact with atoms in the atmosphere, exciting them and causing that unearthly glow.
When a severe CME impacts the earth, it can induce electrical current flow on the wires that make up the transmission part of the power grid. These geomagnetically induced currents can reach levels high enough to cause damage to the equipment that makes up the grid. The large transformers that you see in substations are susceptible to internal heating due to this effect.
This is essentially the same way a power generator works. You move a magnetic field past a conductor and when it cuts through the wires it induces a voltage. Connect that voltage to something and current can flow. This is just happening on a global scale when we talk about geomagnetic storms.
Geomagnetic storms are ranked on a scale from 1 to 5. A level G1 storm causes minor issues, if it is even noticeable. A G2 can cause voltage fluctuations at higher latitudes, but is generally not enough to damage anything or cause power providers to make adjustments. A G3 class storm is strong enough to require power plants to make adjustments as the voltage on the grid varies with the storm. It can also cause false trips on protective equipment, but is generally not enough to damage things.
G4 class storms, such as the one observed earlier today, are severe. The fluctuations can be enough to cause significant voltage control problems and possibly mistakenly trip important equipment, such as large power stations.
G5 class solar storms are extreme. These events are not common, happening approximately 4 days out of an 11 year solar cycle. Most of them are not powerful enough to severely damage grid equipment, but can cause severe voltage swings. Occasionally, such as in the 1989 Quebec blackout, a severe enough storm, or a series of them in quick order, can cause collapse of power grids.
https://www.swpc.noaa.gov/noaa-scales-explanation
The worst solar storm that we know about was also the first one directly observed. The Carrington Event caused the aurora to be visible as far south as the Caribbean. It was so bright that miners in Colorado woke up and started getting ready for their shift. The voltages it induced on the telegraph system were enough to let messages be sent without the batteries hooked up. It even caused sparks to fly from the machines, starting fires.
https://www.space.com/the-carrington-event
If an event as severe as the Carrington Event hits today, large parts of the power grid will go down. Hopefully we have enough warning to do it in a controlled manner, protecting the vital transformers and other equipment so we can restore power quickly following the storm.
We could take action to better protect the grid from CMEs. This would have the added benefit of protecting it from intentional EMPs to a certain extent. Congress has so far refused to fund it beyond establishing a commission to look into it. Such high impact, extremely rare events are hard to push as priorities. The downside to that is something I have mentioned before. If the grid goes down for a year, 90% of Americans will die. That’s a pretty big downside.
Here’s some more links. As always, this is all publicly available.
https://svs.gsfc.nasa.gov/10109
https://www.swpc.noaa.gov/phenomena
https://www.swpc.noaa.gov/communities/electric-power-community-dashboard
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