Since the Carrington event predated satellite data technology, we do not have enough hard numbers to stack it up directly against modern solar flares such as the Halloween 2003 event, which was the largest geomagnetic storm we have ever directly measured.

I have read a little about the numerous ways scientists have tried to estimate the Carrington event, but my limited background in space science means that I could get biased quickly by the few papers I managed to read within the past hours. I want to share what I have gleaned so far to hopefully find someone more familiar with the subject matter to explain/discuss things.

For starter, Curto et al. (2016) estimates Carrington at X45.7 ± 2.2 intensity, which is close to some past estimates (e.g., X45 ± 5 from Cliver & Dietrich (2013)). However, these papers, along with Curto (2020) review, point out that the G5 storm from Halloween 2003 was comparable in magnitude (X35 ± 5 to X45 ± 5).

So, if they are indeed comparable, why are there so many analyses and estimations of the damage to our electrical system should a Carrington-level event happen again? I do not recall the world shutting down in 2003 because of the storm. If there is indeed a massive difference in the strength of the two storms, then what metrics should I be looking at to see that difference?

References:
Cliver EW, Dietrich WF. 2013. The 1859 space weather event revisited: Limits of extreme activity. J Space Weather Space Clim 3:A31. https://doi.org/10.1051/swsc/2013053

Curto JJ. Geomagnetic solar flare effects: a review. Journal of Space Weather and Space Climate. 2020;10:27.

Curto JJ, Castell J, Del Moral F. Sfe: waiting for the big one. Journal of Space Weather and Space Climate. 2016;6:A23.

Comments

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the_fungible_man t1_iuc9n72 wrote on October 30, 2022 at 6:04 AM

There's a difference between a solar flare, and a coronal mass ejection and the effects they produce on or above the Earth. The A, B, C, M, X classes of flares refer to the peak energy measured at a specific X-Ray wavelength. This is omnidirectional high energy electromagnetic radiation that travels at the speed of light. Such radiation does not pose a threat to electrical infrastructure or devices on the ground.

What do pose a threat are the CMEs often associated with solar flares. These are massive clouds of charged particles that generally spread out from site of a flare (a sunspot group) and expand out into the solar system at 1000 km/s or more. When these particles slam into and get trapped by Earth's geomagnetic field, huge electric currents can be produced which in turn can induce currents in transmission lines and other conductive paths on the surface. This can damage the electrical grid.

However, the location of the sunspot on the Sun largely determines the direction in which the CME expands out from the Sun. In reviewing the literature on the Halloween 2003 X28 (X45?) flare, I note that it occurred on November 4, when sunspot group 486 was nearing on the SW limb of the Sun. Any CME associated with that flare was aimed nearly 90° away from the Earth and would have delivered a glancing blow to the Earth, or none at all.

cogitatingspheniscid OP t1_iucaw7e wrote on October 30, 2022 at 6:20 AM

So what would you suggest as a good metric to compare the effects of the two events on Earth? CME net output is probably not good since it would not take into account how much of the CME actually hit Earth?

Nerull t1_iuc8q9a wrote on October 30, 2022 at 5:52 AM

A solar flare and a geomagnetic storm are different things, you cannot directly compare the strength of a flare on the sun and the resulting geomagnetic storm caused by a CME associated with the flare hitting earth.

Importantly, the CME launched by the 2003 flare went away from Earth and didn't hit us.

cogitatingspheniscid OP t1_iucaqfd wrote on October 30, 2022 at 6:18 AM

Thanks, I know that solar flare, CME, and geomagnetic storm are 3 separate things, but I thought that they would have correlated with each other.

So was the G5 storm in 2003 the result of *just* a glancing blow????

harrcs03 t1_iucqg1h wrote on October 30, 2022 at 10:00 AM

If something like Carrington of that happened now with our magnetic field weakening 5% Per decade… That would pretty much be a kill shot for anything electronic and send us back into the Stone Age.

cogitatingspheniscid OP t1_iudwfya wrote on October 30, 2022 at 4:22 PM

Were the Halloween 2003 CME and the 2012 missed CME on the same level? If yes, then they are more common than we want to admit. If no, then what metric can one use to calculate the difference in their power?