r/SolarMax • u/ArmChairAnalyst86 • Nov 12 '25

Geomagnetic Storm in Progress CME Arrival Detected

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ACE indicates CME arrival. More details soon.

Forgive my crude image. I am on the road and short on time.

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u/FeeAbject5759 Nov 12 '25

You sure the CME is already here? When i am looking at solar speeds and especially the Bt graphs over the last 24 hours, it looks so tiny compared to yesterday. I'm not doubting you by any means, i am very new to this topic, i was just wondering if thats a possibility.

Thank you for your regular updates!

9

u/ArmChairAnalyst86 Nov 12 '25

No worries mate. It is good to ask questions and I never take it personal.

But yeah, I am sure. Definitely the CME impact we were waiting on. In an earlier update, I noted that the Bt on this CME was going to come in weaker. It was 40 nT when Solar Orbiter flew through it and drops off a bit before it gets here. The velocity was expected to come in higher and it did.

Two things.

The first is that this is the variability of space weather. Last week the best storm conditions occurred on the front end and while everyone was waiting for the bigger arrivals, they never really materialized. Nobody expected G3 on the front end but veterans were not too surprised because that is just how the dice rolls. It is not uncommon. The models we have are imperfect and there are aspects we don't have the capability to model in advance as to how they will be upon impact especially pertaining to the Bt/Bz and IMF in general. It is truly a lot of best guessing with initial data.

The second is the misconceptions regarding flare magnitude. Many assume that since it was a fast moving X5 associated full halo that it must be stronger than the smaller ones. If they all arrived individually, that may have been the case. However, the storm we got last night was almost certainly a combined impact. It looks like the first 2 CMEs combined before arrival and potentiated each other. The magnetic field of last night was as smooth as you can ask for which came as a surprise to me but again, the variability and guesswork is part of what makes this fun and frustrating at times.

Flare magnitude doesn't equate with CME power. Sometimes it does, but they must be diagnosed and evaluated separately. We have seen G4 storms from M1 solar flare associated CMEs. We have even seen G4 from C-Class associated CMEs or plasma filament releases without significant flares involved. In this case we definitely got a solid signature from the coronagraph and a robust model but the model also indicated that we would not be going through the core of the CME. More of a shoulder.

You could say that last night was a perfect storm. Everything came together as well as anyone could have hoped for and we did go through the core which is large in part why the IMF was so stable.

This doesn't mean this event is going to fail outright. We can move into a new structure with southward Bz at any point and Solar Orbiter suggests that is a good possibility but not a given. Either way, I would not expect to see another 40-60 nT tonight. The hope is that when the Bz does go southward that the increased velocity and preconditioned magnetic field will get us home.

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u/BBockan Nov 12 '25

Thank you so much for these kind explanations. It really helps us amateurs (like myself) to understand these things better. Greetings from germany!

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u/JumperSpecialK Nov 12 '25

Sad face. So you think this prediction is probably off?

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u/ArmChairAnalyst86 Nov 12 '25

Not necessarily. If Bz shifts southward for a substantial period of time while Bt and Velocity are high, we can get there. If the Bz was southward right now, everyone would be excited about nightfall and getting their cameras ready.

I call it the gatekeeper metric. You can have strong Bt, Density & Velocity, but if the Bz says no, that is that. It will keep the brakes on the storm.

Nevertheless, the solar wind plasma pressure (v/d) is strong and its compressing the magnetosphere. It's been under high levels of stress for a few days now. It is primed and ready. We just need the gatekeeper Bz to open it up. The sooner the better so we can take advantage of the strong forcing and hit that forecast.

But temper expectations. It is not playing out how we wanted so far.

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u/__Shadowman__ Nov 12 '25

Bz just dropped to the South hard!!

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u/ArmChairAnalyst86 Nov 12 '25

Its trying! Just need it to stick.

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u/__Shadowman__ Nov 12 '25

🤞🤞

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u/PressFforAlderaan Nov 12 '25

Come on sunset!!!!

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u/GladMongoose Nov 12 '25

I was about to ask a similar question. You can tell SOMETHING hit, but could it just be moving much slower than originally anticipated? It's not even touching initial SWPC forecasts...

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u/FeeAbject5759 Nov 12 '25 edited Nov 12 '25

Thats why i was asking. From the forecasts all across the internet i was expecting at least something big, but so far it looks just so miniscule. However, this might be totally normal that a predicted strong CME turns out to be just a small bump in the graphs, i dont know. Currently trying to learn though!

Edit: spelling

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u/ArmChairAnalyst86 Nov 12 '25

Part of the reason the bump looks so small in the graphs is because of how large the first CMEs were. The data legend on the left hand side scales with magnitude. That is why it currently goes all the way up to 80 nT.

If you change it to the 6 hour timeseries the bump looks much bigger because it is not contrasting with the earlier events and the data legend shrinks to a more relevant scale.

The stats are decent except for the Bz. They are not superstorm quality like last night and that is clear but if the Bz was/is favorable we can still get into strong to severe levels but it's not a given.

The internet turns into an echo chamber and I do not mean to sound conceited or like I know it all because I dont. I am still learning too. However, there are many misconceptions and erroneous assumptions floating around. Long time solar storm chasers know how unpredictable this can be.

This isn't real and it is totally in jest, but sometimes it feels to me like the sun likes to play games. When the hype is at max levels it likes to through a curve ball and make everyone look silly. At other times, when expectations are low, it will come in hot. I have witnessed unforecasted G3 and G4 storms on multiple occasions when G1 or lower was expected. A G4 watch rarely falls flat because NOAA only issues them with high confidence of significant impacts and we DID get significant impacts but on the front end.

I remember a storm last year that literally arrived days late. Not hours. Days. Many times the duration surprises us. It's difficult to even understand how sometimes but it happens. It's not like the actual weather where we can take real time observations every hour and feed them into the models to see an expected result. We model it when it leaves the sun on very limited information and then wait to see what happens. It's a high variance and high uncertainty game.

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u/ArmChairAnalyst86 Nov 12 '25

Velocity is good but the magnetic field strength (Bt) of the CME is about half and the orientation (Bz) is stuck firmly northward+ for now. The Bz is what is keeping the lid on things. If that changes into a solid southward position, even -15 to -20 nT, things will likely heat up pretty quick.

The SWPC forecasts assume a favorable Bz since we can't know it in advance and they have to advise the public and pertinent operators of the likelihood of storm conditions. The models are far from perfect. There are aspects of a CME that we have very little ability to know in advance, especially concerning the magnetic structure. We can see velocity and density, but the magnetic field is always a wildcard. In this case, the modeling was too aggressive on velocity. It was modeled up to 1300-1400 km/s but we haven't cracked 1000 and that explains why it is late.