Most planets have magnetic poles that align pretty well with their geographical ones. On earth, for example, the magnetic dipole field is tilted about 11 degrees from the rotational axis. As far as I understand, this is a consequence of how the magnetic field is generated. While I am by no means an expert on dynamo theory, here's the gist of what I understood: convection current in the molten outer core generate magnetic fields. The Coriolis effect aligns them into (vaguely) helical flows and thereby aligns the fields into a planet-wide magnetic dipole field. Similar processes also apply to gas giants, but I don't think they are relevant here as the planet in question needs to be habitable for human-like life.
On Uranus, however, this tilt between rotational axis and magnetic field is 59 degrees. This may be because Uranus' magnetic field is generated in a completely different way, closer to the planets surface.
What could cause a stable tilt in the magnetic field of a planet on a similar scale (>35 degrees) while the planet still needs to fulfill the following criteria:
- It needs to be habitable to life, including intelligent life
- The tilt of the rotational axis should be similar to earth's, to allow for seasons
- If necessary, no tides or heavier tides than on earth are acceptable, as long as they still allow for seafaring with late medieval technology (wooden ships)
- The day/night cycle on this planet should be similar to earths (so no tidal locking with the host star or something similar. Longer or shorter days are acceptable as long as it's not excessive)
- "stable" in this context means that the magnetic poles should not move by an appreciable amount over thousands of years, so that many generations of intelligent life would see a compass point basically in the same direction. Pole reversals, like we see on earth, are acceptable.
Here is a list of things I have already thought about, and why I discarded them. All of them would be acceptable, if you can make them work somehow:
- A natural satellite or binary planet with its own magnetic field (from what I can tell, they would either need a ridiculously strong magnetic field or be very close to affect the magnetic field of our planet meaningfully)
- A planetary ring (Even though in our solar system only the gas giants have rings, smaller/less massive planets could have rings, too. However just having a ring made of ice/rocks would not affect the magnetosphere of the planet on a large scale. Could they be of a material that influences the magnetic field more?)
- Ring currents (While ring currents can affect the magnetosphere, they are dependent on it in the first place, as they are created by charged particles trapped in the magnetosphere. I see no way to arbitrarily turn the ring current)
- A solid iron core that cooled down in the presence of a strong magnetic field. This would lock the magnetic field of the core in place and essentially turn it into a permanent magnet. This magnetic field is independent of the axis of rotation and can therefore be misaligned as much as we want. (However, there are some open questions I cannot find answers to: What could reasonably create a magnetic field strong enough for this? Is the resulting field of the permanent magnet considerably weaker than that generated by a molten core? And can a planet with a frozen core harbor life? The Wiki on Planetary habitability mentions a molten core to be at least conducive to life because it is responsible for plate tectonics. Can we go half way and have a big solid inner core responsible for the magnetic field tilt and a thinner molten outer core for tectonics?)
- A completely different way to generate the magnetic field that allows for such a tilt (I do not know what this could look like, but as long as the list of requirements above is met, anything goes.)
Any solution that might work and is not on this list is, of course, also welcome!
I have, so far, not talked about the reason our world needs this tilt in order to make this post relevant to a wider range of world-builders (I am sure you can come up with many interesting ways such a tilt affects the world and its inhabitants) But for anyone interested, I will outline my own reasons here: This medieval fantasy world has similar climates as earth with frozen poles and warmer climates closer to the equator. With a tilt in the magnetic field, the magnetic poles fall into more temperate climates, which I need. A lot of conflict in the story arises from a religious group seeing this magnetic pole as spiritually important as all compasses lead there and auroras can commonly be seen. They believe this is the origin of the world from which their Creator-God built outward.
This is my first ever post on any StackExchange. I hope I followed any guidelines correctly. I'd appreciate any comments pointing out where I go wrong. I'd also appreciate comments correcting any grammatical errors as english is not my first language.
Thank you for your help!