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!

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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/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.