Comment by jjcm
12 hours ago
If anyone is interested in what "G4" means in context, here's the scale: https://www.swpc.noaa.gov/noaa-scales-explanation
12 hours ago
If anyone is interested in what "G4" means in context, here's the scale: https://www.swpc.noaa.gov/noaa-scales-explanation
Interestingly, there are about 100 events of this severity (G4) per cycle, and a single cycle lasts 11 years. This means there are about nine G4 events on average per year.
Note, however, that the solar cycle [0] is so named due to its minimum and maximum: the most severe events will be clustered around the maximum, rather than spread out over the whole cycle (as your comment suggested) - so the "nine G4 events on average per year" is mathematically true but not so helpful.
[0]: https://en.wikipedia.org/wiki/Solar_cycle
The scale seems capped at a pretty low upper end? It feels like with all the mindbogglingly huge numbers usually involved when talking about space, there must be much, much worse events possible. Is it just that we don't know enough about them due to lack of experience that these aren't included?
https://en.wikipedia.org/wiki/Carrington_Event
But having been in 1859 we only have estimates on what the consequences would be in the modern world. But pretty grim at the looks of it.
G4: " Induced pipeline currents affect preventive measures, HF radio propagation sporadic..."
G5: " Pipeline currents can reach hundreds of amps, HF (high frequency) radio propagation may be impossible in many areas for one to two days..."
Sam Altman has entered an agreement to acquire all future G4 and G5 energy
Waiting until it's like a G6, Like a G6
Now I'm feelin' so fly like a G6
Thanks, really had to listen to the song.
https://www.youtube.com/watch?v=DWRJC8ap9B4
"Cool! What's G13 do?" - Bill Hicks
Looks like G5 is the highest level and the scale system is used by NOAA.
>"Cool! What's G13 do?" - Bill Hicks
I hear that bit in my head every time a new plane or weapon designation is announced, glad to hear it stuck with others too.
HF propagation is flaky at the best of times. It's affected by the day/night cycle and by the weather.
"Free Energy!"
That's the nice thing about solar power, but it's still a limited time offer
We are at kp 8.67. The Carrington event was a kp 9
I am not an expert, but it’s worth noting that the kp index has a maximum value of 9. So though the Carrington event had a kp of 9, its intensity on the related (but not capped) HP30/HP60 scale [1] would likely have been higher. [1] https://kp.gfz.de/en/hp30-hp60
Queue Chernobyl documentary clip measuring the radiation as low because that’s as high the meter went
7 replies →
Disturbance storm time index (DST) is a better measure of peak intensity as KP is just a weighted average of the intensity from the last three hours across monitoring stations.
The May 2024 G5 electrical storm had a peak measured DST of −412 nT: https://en.wikipedia.org/wiki/May_2024_solar_storms
The Carrington Event had an estimated peak DST of −800 nT to −1750 nT, but no one really knows: https://en.wikipedia.org/wiki/Carrington_Event
This is also related to weaker solar events leading to stronger Earth storms due to Earth's weakening magnetic field.
Have we been having these more recently?
I don't ever recall seeing these in the news so frequently. It feels like there are several a year now. A decade ago, never.
And I also never remember seeing Aurora at my latitudes.
Do we just have better sensing now, or is there some cycle on a period longer than a few years? Or maybe I'm crazy and just never noticed.
Mid to late 2025 was the peak of an 11 year solar cycle (25th one since we've started keeping track). We're on the trailing end of that peak activity now, which is why the past year/several months has seemed so active compared to recent years past, and should decrease significantly (in frequency and intensity) as 2026 progresses.
There was also a fairly significant geomagnetic storm back in November of 2025 as well.
You can see the data here at NOAA's Space Weather site https://www.swpc.noaa.gov/products/solar-cycle-progression
We've just passed the 11 year peak - the sun spot activity has a period of around 11 years.
> Biological: Unavoidable radiation hazard to astronauts on EVA; passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.
Anyone have a sense of magnitude for this advisory? How much more radiation should an airline passenger expect to receive during a G4 event than normal?
roughly up to 5-10 times the normal dose.
sounds "it's okey" ?
1 reply →
Looks like we get these for about 60 days for periods lasting 11 years.
This was an S4 event, however.
Belay that. The G-value was high too.
so more of a 'bad storm here and there' level?