The magnetic poles are close to the rotational poles because the core rotates along the same axis as the surface of the planet.
The magnetic poles tend to reverse themselves every few hundred thousand years or so (it’s kinda random, anywhere from about 100,000 years to 1 million years, give or take). We’re not sure exactly what happens during these reversals. It may be that the poles end up pointing in different directions like towards the equator and/or elsewhere. The poles may be weaker, or the entire magnetic field may end up kinda chaotic and there may not be any strong poles in any direction.
We’re also not sure how long the reversals take to complete. Our best guesses are on the order of a few thousand years.
There was a mini-reversal about 41,000 years ago called the Laschamp event. The reversal took about 250 years to complete and only lasted for about 440 years. The magnetic field was significantly weakened during the transitions.
Wikipedia article on the Laschamp event:
Wikipedia article on geomagnetic reversals:
Anyway, while north and south tend to flip themselves magnetically on occasion, in the long term they always end up aligned with the rotational axis of the Earth.
Somewhat related: the north pole of one magnet pushes away the north pole of another magnet. The north pole of one magnet attracts the south pole of another magnet. So the earth pole that attracts north poles on magnets (in compasses) is actually a magnetic south pole.
Also, if Wikipedia is to believed, the line connecting the two poles doesn’t go through the center of the earth: one is at ~ 85 north, the other at ~ 64 degrees south.
So the physical reason is that spin will create spinning columns aligned with Earth’s axis, and those columns induce the magnetic field. Beats me how a reversal can occur that way, but the evidence is there that it does happen.
A similar process occurs in the Sun, but on a much shorter timescale, and much more regularly (mostly because the fluid of the sun is less viscous than the Earth’s core). The Sun’s field reverses every 11 years, and while it’s reversing, it’s a very messy and weak field with lesser poles all over the place. It’s probably similar when the Earth reverses, though we’ve never yet observed it.
I see the wikipeida article mentions there was increased radiation levels on the earths surface during the Laschamp event. If this was to recur, or even a larger such reversal, what is the anticipated impact on human health?
Minuscule to the point of irrelevance, or heavily increased rates of radiation induced issues like cancer and so forth?