# Is there a physical reason why magnetic north is generally north?
**URL:** https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212
**Category:** Factual Questions
**Created:** [December 23, 2015, 7:58pm UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212 "2015-12-23T19:58:51Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Sigene](https://boards.straightdope.com/u/Sigene)
#### Post date: [December 23, 2015, 7:58pm UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/1 "2015-12-23T19:58:51Z")
I think I understand that a spinning liquid metal core naturally generates a magnetic field.
Is it pretty much a physical necessity that the magnetic poles are very close to the axis of rotation? or is it simply more of a coincidence?
Could we have an expectation that the magnetic poles can be any latitude on the globe, like even near the equator?
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### Author:  [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)
#### Post date: [December 23, 2015, 8:18pm UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/2 "2015-12-23T20:18:25Z")
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:
> **[Laschamp event](https://en.wikipedia.org/wiki/Laschamp_event)**
>
> The Laschamp or Laschamps event\[note 1\] was a geomagnetic excursion (a short reversal of the Earth's magnetic field). It occurred between 42,200 and 41,500 years ago, during the end of the Last Glacial Period. It was discovered from geomagnetic anomalies found in the Laschamps lava flows in Clermont-Ferrand, France in the 1960s.
> The Laschamp event was the first known geomagnetic excursion and remains the most thoroughly studied among the known geomagnetic excursions.
> Since its discovery, the m...
Wikipedia article on geomagnetic reversals:
> **[Geomagnetic reversal](https://en.wikipedia.org/wiki/Geomagnetic_reversal)**
>
> A geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with geographic north and geographic south). The Earth's field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons.
> Reversal occurrences are statistically random. There...
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.
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### Author:  [@iljitsch](https://boards.straightdope.com/u/iljitsch)
#### Post date: [December 23, 2015, 9:49pm UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/3 "2015-12-23T21:49:27Z")
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.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [December 23, 2015, 10:17pm UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/4 "2015-12-23T22:17:28Z")
[From wiki](https://en.wikipedia.org/wiki/Dynamo_theory):
> [@](#):
>
> In the case of the Earth, the magnetic field is induced and constantly maintained by the convection of liquid iron in the outer core. A requirement for the induction of field is a rotating fluid. Rotation in the outer core is supplied by the Coriolis effect caused by the rotation of the Earth. The Coriolis force tends to organize fluid motions and electric currents into columns (also see Taylor columns) aligned with the rotation axis.
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.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [December 24, 2015, 12:36am UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/5 "2015-12-24T00:36:36Z")
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.
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### Author:  [@Richox](https://boards.straightdope.com/u/Richox)
#### Post date: [December 24, 2015, 12:53am UTC](https://boards.straightdope.com/t/is-there-a-physical-reason-why-magnetic-north-is-generally-north/741212/6 "2015-12-24T00:53:58Z")
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?