Planetary Magnetic Field Question

[keithcurtis]

Given:

The earth, through means irrelevant to the question, has had its axis of rotation changed. The new Equator is roughly the old 100°W meridian, and the new poles are the equatorial Atlantic between S. America and Africa, and the Equatorial Pacific, around the Marshall Islands. I have a good enough grasp of general climate theory to make a new climate map that doesn't suspend disbelief to the layman observer. However, I do not have a sufficient grasp to know what would be the effect on the magnetic field.

 

Right now, my assumption is that the planet was re-oriented as a whole, that the core moved along with it. This does not have to be so. I know that the magnetic North (and I presume the overall magnetic field) wanders over the passage of time. If the magnetic axis roughly matches the rotational axis, as it does now, I assume that the effect on my climatic assumptions would be minimal. However, assuming that the magnetic field moved along with the earth, and that magnetic north is now equatorial, rotating every 24 hours, what might be some observed phenomena? Would this seriously impact the livability of life on earth? Is it even possible?

 

Please note, I'm not looking for ecological consequences. This was an apocalypse, and its effect on species and life around the world has been dealt with. I'm looking for the long-term effects on the nature of earth's surface environment. Would there be equatorial auroras? High radiation areas? Would solar flares and winds be more of a hazard? Greater temperature fluctuations? Would there be effects on the compass, beyond pointing to a fixed spot on the equator? Would this be advantageous or disadvantageous to navigation?

 

Any ideas?

 

Keith "sprucing up the Savage Earth" Curtis

[Cancer]

Re: Planetary Magnetic Field Question

 

You'll get aurorae around the magnetic poles, wherever those are. Aurorae are caused by solar wind particles making it down to the upper atmosphere and making the gas aoms there fluoresce. The magnetic field is usually strong enough stand these particles off. Except, with the usual dipole field, those particles are actually funneled into ring-shaped areas around the magnetic poles at the top of the atmosphere.

 

If the magnitude of the magnetic field is more or less the same after changing the world's orientation, then I don't think it's any less effective in standing off radiation.

 

FWIW, the geomagnetic field reverses fairly frequently, in a geological (not human) sense. Right now the main magnetic field of Earth is weakening at a detectable rate, and there is strong suspicion that we are heading toward another reversal event. (The timescale for this is much longer than a human lifetime ... on the order of the next million years or so.)

 

IMO having the magnetic pole on the dynamical equator would actually aid navigation. Getting your latitude is the easy part of navigating by the stars; the magnetic compass as it is now is an aid to that, since it helps you tell which way is north (maintaining your bearing) while it's cloudy. If the compass points toward the magnetic pole and that's on the equator somewhere, then you get an indirect handle on longitude from that, something you didn't have before. To see what I mean, start with a globe with only lines of latitude drawn on it. Now pick the magnetic poles, and in a different color ink, draw circles of "magnetic latitude", that is, equal distance from the magnetic pole. One that's done, look at it, and note that on any given line of ordinary latitude (except the equator, if you put the magnetic poles on the equator), there is a variation in the direction of "magnetic west" (the direction toward the magnetic pole) everywhere on the line of latitude. That means that if you know your latitude (which you do from the stars), then the difference in direction between celestial north and magnetic north provides you with some information about where you are on your circle of longitude. Depending on where you are, it may not be much information, but it's more than the pre-1600 navigators had.

 

The geodynamo is an insanely complex bit of physics, but it works because a part of the planet's core is liquid, electrically conductive, convecting, and rotating. Because it's liquid, it wouldn't necessarily be strongly bound to the solid part of the Earth by whatever cataclysm knocked the mantle/crust sideways. There's a good deal of coupling between core and lithosphere, of course, but I'd need to look up some stuff and push numbers around to say more.

[Maur]

Re: Planetary Magnetic Field Question

 

Actually if the magnetic poles were down on the equator then the magnetic field would not be as protective of the Earth as it is now. As each pole rotated towards the sun that hemisphere of the planet would be more exposed to the radiation as a whole. The field as it currently is positioned protects the Earth all day long because the field is perpendicular to the arriving particles causing them to go up and around (or down and around) the planet. The aurorae that we currently see as rings on the planet wouldn't be rings anymore as the particles wouldn't be creating the effect by following the field back down, but driving straight into the atmosphere.

 

http://en.wikipedia.org/wiki/Earth's_magnetic_field

[Curufea]

Re: Planetary Magnetic Field Question

 

The field as it currently is positioned protects the Earth all day long because the field is perpendicular to the arriving particles causing them to go up and around (or down and around) the planet.

 

Mostly perpendicular : +/- 23.4 degrees for the Earth's axial tilt from the plane of the ecliptic and +/- 11.3 degrees for the magnetic field's axial tilt from the Earth's.

[Beast]

Re: Planetary Magnetic Field Question

 

saw this one a few weeks ago

it should be a good start for you

the pole flips happen on average every 175,00 yrs

last 1 happened over 750,000 yrs ago

could be as fast as 6 days or a 1000 yrs

if it takes over 3000 yrs the planet is toasted

 

http://www.netflix.com/Movie/Magnetic_Storm_Nova/60035188?trkid=189530&strkid=1121010385_0_0

[Old Man]

Re: Planetary Magnetic Field Question

 

Actually if the magnetic poles were down on the equator then the magnetic field would not be as protective of the Earth as it is now.

 

Which provides a nice justification for Savage Earth furry mutants, assuming you use comic-book radiation and not the real thing.

[keithcurtis]

Re: Planetary Magnetic Field Question

 

Which provides a nice justification for Savage Earth furry mutants' date=' assuming you use comic-book radiation and not the real thing.[/quote']

 

Nah, I use another explanation entirely.

 

Keith "I'm thinking of maintaining a polar magnetic axis" Curtis

[Captain Obvious]

Re: Planetary Magnetic Field Question

 

Not that I'm a geologist or a physicist or anything, but it seems to me if the global tilt was sudden enough, the new pole would be more or less where the magnetic pole was, although there might be some wobbling of the magnetic pole if the tilt wasn't quite as sudden as that pulling-the-tablecloth-from-under-the dishes trick. And if the magnetic pole does wander somewhat for a while, it might be enough to create a tradition of not really trusting compasses 100%.

[Bygoneyrs]

Re: Planetary Magnetic Field Question

 

Well if your asking about a "mantle Slip", that is said to happen ever so often, then

the end effect would be Global in effect. The Ice caps would totally melt and build

up in the new location, thus the Earth would be in a new Ice Age that would last

like 1000+ yrs. Most likely the places where currently are the high tech locations

would become the new Ice caps, so alot of tech and knowledge would be lost.

It wiuld be a true PAH campaign world for sure!

 

Penn

[rmccarty4]

Re: Planetary Magnetic Field Question

 

If I understand the geophysics of the magnetic poles correctly, the magnetic pole "prefers" to align near the rotational axis -- the dynamo works best that way. If the magnetic pole were near the equator, the rotation of the earth would spin the magnetic pole through space, making a (relatively) rapidly rotating magnetic field, which would exert significant electromagnetic force. It wouldn't be stable, which is why the magnetic N tends to align with either rotational N or S.

That rapidly changing magnetic field shouldn't collect charged particles in the way our current magnetic fields do, so I wouldn't expect equatorial auroras. OTOH, it might allow charged particles (a form of radiation) to bathe the earth, since they won't be diverted by a stable magnetic field. I believe that might cause the Earth's atmosphere to be scrubbed away by the solar wind.

Apparently, Earth's magnetic field may be weakening; if it continues to weaken at the perceived rate, Earth might lose much of its atmosphere within a thousand years.

[rmccarty4]

Re: Planetary Magnetic Field Question

 

Separate question, 'cause now I'm curious: did Earth start rotating about a different axis with the same orientation relative to solar system north (such that it's still spinning about an axis that's perpendicular to its orbit around the sun), or is the new axis closer to parallel to the solar system plane of rotation, like Uranus? Seasonality is obviously going to be greatly increased for the latter scenario, and even if the magnetic pole is close to the rotational pole, the polar area would get scrubbed by solar wind & radiation.

I know you wrote you'd addressed the climate, but I'm wondering about your take on said climate.

[SteveZilla]

Re: Planetary Magnetic Field Question

 

To add to the overall "mix" of tipping the Earth over, is the issue of the mantle's hot spots and convection zones (which AFAIK drives plate tectonics). If the crust of the Earth is shifted greatly from it's associations with the Mantle, you would likely see many volcanically active locations go cold, and other areas where there has been no recorded activity sprout volcanoes and fissures.

 

Regardless of whether or not it goes dormant, Hawaii would wind up very near one of the new geographic poles, and thus get buried in ice.