Effects of high magnetism?

Question

I have a head-world idea where one of the planets in it has four magnetic poles. It is a desert rocky planet with carbon based lifeforms on it (mostly underground or in bio-domes). What would the effect of such high magnetism be?

The deserts are made out of both magnetically charged and non-charged rocks and minerals, like purple garnets, bituminous sands (oil/tar/petroleum/asphalt), clay, magnetite, iron-nickel, ferberite,and pyrrhotite.

Other information: The water on the planet is underground. Each pole has a passage to the layer of the planet with the ocean. This is because the temperature fluctuates from 120C° to -90C°. This planet has two moons, the smaller moon orbits the larger moon, which orbits the planet. The planet's radius is 3058 km. It orbits a class A white supergiant.

How much magnetic force would be needed to make noticeable strange effects? What would the effects be?

Also please let me know if things aren't possible. I'm mostly running with ideas right now and nothing is set in stone.

Answer 1

I'm having a hard time picturing all the implications. Here is a completely-random list of implications that come to mind right now, not all about the magnetism itself.

1) as my comment above says, four poles is nearly impossible, no matter how strong your magnetism. I can't imagine how the poles would develop naturally, but even if a planet started with four it would end up with two eventually. If you want four poles you would need to do quite a bit of work to justify it. The best I could imagine is stating that the poles are degrading into 2 poles, but that it will take awhile for that to happen on planet scale so you currently have 4 poles, even if it isn't stable.

2) If your people live underground you will need to address this. Most importantly where do they get energy? Most energy we use comes, directly or indirectly, from sunlight. Do they still have solar panels, do they relay on Geo-thermal etc. Perhaps they could try to draw power out of the magnetic potential energy itself, though I currently can't think of a reliable way to do so.

3) water is magnetic. Really it's true, thanks to good old hydrogen bonds (If you asked why something happens in chemistry class and have no idea say hydrogen bonds, your get it right half the time lol). If you start your tapwater and hold a magnet next to it it will curve slightly towards the magnet. This could be mentioned that the water flows underground in a pattern that predicts the magnetic poles on level ground. I don't think it changes the world in any large ways, but it would be an interesting tidbit of world building to mention.

4) It seems plausible that your species would evolve with the ability to sense magnetism, much like birds do today when migrating south. It may be mostly subconscious, but in a world with such magnetic potential I can see many evolutionary advantages to doing so. This would in turn strongly effect how your creatures evolve and act. Maybe they don't see light, living underground, but can sense magnetism and changes in magnetic pull?

Answer 2

Actually, the strength of the field would change at the planet's surface. If we model the field as a dipole, it is described by the equations $$B_r = -B_0 \left(\frac{R_E}{r} \right)^3 \cos \theta$$ $$B_{\theta} = -B_0 \left(\frac{R_E}{r} \right)^3 \sin \theta$$ $$|B| = B_0 \left(\frac{R_E}{r} \right)^3 \sqrt{1+ \cos^2 \theta}$$ where $R_E$ is the radius of the Earth and $r$ is the distance from the Earth's center. So the field's strength on the surface would be greater than that of the same field on earth's surface. Admittedly, this field is a quadrupole field (see below), but the same principles should apply.

Anyway, I talked about this type of magnetic field in my answer here, stating that a planet with two cores might very well have four magnetic poles. If the Earth had two cores, then the currents should create a quadrupole field, with poles at the Equator and the North and South Poles. I'm not going to copy-and-paste from that answer, but I'll list some of the effects:

• A magnetosphere with a different shape, which could either help or hurt the ability of the magnetosphere to better protect the Earth from charged particles from the Sun.
• Auroras near the equator

It's hard to tell exactly whether these would be good or bad for life on the planet. Chances are, though, you wouldn't see any drastic effects. Although the magnetic field on the surface would be stronger, because the radius is smaller - not because there are four poles.

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Do you mind if I comment a little on the rest of the setup? I'll be honest - it's unlikely. It's not likely that a planet would evolve life within the lifespan of a class A supergiant. They live for a short while and then die spectacularly. Is it necessary for the star to be of this kind? I'd suggest something a bit smaller, less massive, and longer-lived.

I'm not sure just how likely the moon-caption scenario is. After all, a small radius means the planet is less massive, and less likely to have moons. To have a moon big enough to have another object orbiting it would require a large primary moon, and so most likely a large planet. Does the size of the planet matter?

Each pole has a passage to the layer of the planet with the ocean. This is because the temperature fluctuates from 120C° to -90C°.

How dos these passages exist? I would think that tectonic effects would have closed them up really quickly. I'm not sure how the temperature plays into it; there shouldn't be much expansion/contraction of the crust because of temperature swings.

I apologize if it seems like I'm being harsh, but there is a reality-check tag here, so I think that handwavium wouldn't be a good option.

Answer 3

The habitability of your planet will be determined not by the magnetic fields, but rather by the conditions required to generate such fields.

Ultimately, the magnetic fields of a planet are driven by convective cycles in the molten metal interior of the planet. These cycles are complex, and generate complex magnetic fields with many poles. However, as you move further away from a planet, the strongest two poles dominate the others and generate a magnetic field that only appears to have two poles. (Unless you measure it really accurately.) On Earth, the distance required for the other poles to be less noticeable is less than the radius of the Earth. On the sun, this is not the case.

While the sun is still dominated by a deep helical dynamo that generates most of the magnetic field, at the surface, local convective effects are stronger than this dynamo and result in localized magnetic fields and poles at the surface of the sun. This is due to strong convective behavior close to the surface, which is not present on Earth. Our planet has something like 8 smaller poles created by convective currents in the mantle, but they're not as strong as the primary magnetic field at the surface. This is in part due to the coriolis force organizing the convective processes in the Earth in the same direction, and in part due to the depth of the mantle on Earth, and its relatively low levels of activity.

If you want to increase the strength of the magnetic field and get more poles, a good start would be to increase the convective activity of the Earth and to reduce the coriolis force: i.e. make it more volcanically active and spin much slower. While space faring travelers would still read a dipole on their sensors, this would make inhabitants on the surface experience a much more complex magnetic field, in which fields driven by local convection are stronger than the global dipole at the surface.

Creatures living on the surface would have to deal with a significantly more polluted atmosphere as a result of the volcanoes, although a water cycle driven by cooling on the dark side of the planet would help clean many of the pollutants out of the atmosphere. Their lives would be dominated by a long daily cycle:The planet would freeze at night, but as it turned towards the sun, all of the water would start to melt, resulting in a period of several earth days in which they could enjoy the morning. Of course, it would then start to get too hot, with the lakes and rivers beginning to boil away, leaving an empty desert too hot to sustain life. Animals would have to find a way of sheltering through the day until it darkened and began to cool, at which point all of the boiled off water would start to condense, before coming down in torrential rains. Finally, during the long night, the planet would continue to shed heat and eventually freeze. Surviving this cycle would be a challenge, although living deep in the oceans might help mitigate the temperature swings.

The location of the poles would also be chaotic, so animals wouldn't be able to use them to guide navigation. They might, however, follow a periodic cycle. This happens on the sun, and results in the Wolf sunspot cycle. Since they're intrinsically tied to the levels of convection, life on the planet might be able to internally sense the magnetic field changes and use them to gauge when the volcanoes are likely to be more or less active.

Answer 4

One admittedly tangential point: Extremely intense magnetic fields can cause enormous fatigue and (probably) strain on the heart.

How? because blood is saltwater, highly conductive. Moving a conductor through a magnetic field creates electrical current; and, more to the point, requires physical force. Your heart, in an intense magnetic field, is working extra hard just to get the blood to move.

It sounds ridiculous, perhaps, but my aunt was actually subject to this. Her office at the National Bureau of Standards (now NIST) was on the floor directly below a lab in which a researcher was creating high-intensity magnetic fields. By the end of the day she and her officemate were about ready to pass out. This went on for a while, until the researcher took a day off, and the exhaustion did not occur. Someone figured it out, they moved their work location, and the tiredness went away for good.

Now, I seriously doubt that any planetary magnetic field could be anything like this. The mechanism for this kind of intensity would probably not be physically possible in a planetary core. (She told me the field intensity in gauss; I don't remember what it was, only that it was impressively large.) So probably this particular issue is not important. However, it's an interesting example of an extreme magnetic effect that would be very hard to anticipate. Possibly this would be of interest to you.