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Comment by sidcool | Hacker News Reader

Apparently this happens every 11 years. Nothing to panic, but an interesting astronomical phenomena nevertheless.

Part of me kind of wishes that this had some trivial, totally safe and innocuous consequence that you could still appreciate somehow with a Mr. Wizard type experiment.

So this is an alternating current, but with a cycle time of 22 years instead of a fraction of a second?

No, it's a chaotic system that is quasistable for an average of 11 years at a time before it flips to the opposite orientation with respect to the spin axis. The Earth's magnetic field, generated by currents in the liquid outer core, is a similar magnetohydrodynamic system that has no apparent periodicity.

Disclaimer: I worked on the solar magnetic field for two summers.

Whether the sun is chaotic in the technical sense (i.e. the butterfly effect) is still open to question [1]. The solar magnetic field is poorly understood. In the 1980s, everybody thought that a particular model (mean-field dynamos IIRC) had it all figured out, but new observations from helioseismology showed them wrong. Wikipedia has a good article on the solar cycle: https://en.wikipedia.org/wiki/Solar_cycle My advisor wrote a more technical overview: http://solarphysics.livingreviews.org/Articles/lrsp-2010-3/a...

[1] See: https://en.wikipedia.org/wiki/Chaos_theory#Distinguishing_ra...

So astronomical objects are classifiable under a magnetic AC/DC onotology? Wow. Seems like dualism dies hard.

How can you get that from that reply? He specifically said they are not.

Err, I'm not sure how your brain works but it's obviously different to mine. Fear not, in heterogeneity lies strength!

The last time a geomagnetic reversal occurred on Earth was 780,000 years ago (with a possibility of a brief one occurring 41,000 years ago) [1]. I wonder what it will feel like when it happens again...

[1] http://en.wikipedia.org/wiki/Geomagnetic_reversal

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