Earth's Magnetic Field

[Coyote]

Found here at MSNBC, an article on changes in the Earth's magnetic field.

It got me to wondering some things with regards to these tidbits:

A new model uses satellite data from the past nine years to show how sudden fluid motions within the Earth's core can alter the magnetic envelope around our planet. This represents the first time that researchers have been able to detect such rapid magnetic field changes taking place over just a few months.

Okay, so the magnetic field can change rapidly-- we're not looking at a "Geological Time Scale" here where things will happen hundreds of thousands or millions of years from now, but events that can take place in under a year's time.

Bubble bobble
The Earth's magnetic field extends about 36,000 miles into space, generated from the spinning effect of the electrically-conductive core that acts something like a giant electromagnet. The field creates a tear-drop shaped bubble that has constantly shielded life on Earth against much of the high-energy radiation flowing from the sun.

The last major change in the field took place some 780,000 years ago during a magnetic reversal, although such reversals seem to occur more often on average. A flip in the north and south poles typically involves a weakening in the magnetic field, followed by a period of rapid recovery and reorganization of opposite polarity.

Some studies in recent years have suggested the next reversal might be imminent, but the jury is out on that question.

The Earth's overall magnetic field has weakened at least 10 percent over the past 150 years, which could also point to an upcoming field reversal.

Okay, so we could be looking at a magnetic field reversal (or collapse?) potentially within our lifetimes? And we'd have a few months to prepare?

What would this mean to us on Earth? Would Earth become a scoured, irradiated and blasted landscape of radioactive desolation? Or would we even notice, beyond a statistical spike in cancer rates among people who lived through it? And would a period of "rapid recovery" be on the same scale as the collapse (a few months) or would it take hundreds/thousands of years?

[Broomstick]

Okay, so we could be looking at a magnetic field reversal (or collapse?) potentially within our lifetimes?

Certainly

And we'd have a few months to prepare?

Maybe, maybe not. No one has actually ever seen a reversal, no one really know what the warning signs would look like, and no one knows how fast they actually occur. It could take centuries, decades, years, months, weeks, days, hours... no way to be sure.

What would this mean to us on Earth? Would Earth become a scoured, irradiated and blasted landscape of radioactive desolation?

Absolutely not. There is no indication of that strong a correlation between mass extinctions and magnetic reversals.

Or would we even notice, beyond a statistical spike in cancer rates among people who lived through it?

Maybe not even that. Or maybe we all get sick and die prematurely.

And would a period of "rapid recovery" be on the same scale as the collapse (a few months) or would it take hundreds/thousands of years?

Again, no one knows. It all depends on how fast a new global magnetic field establishes itself.

[Bilbo]

A reversal is just what it sounds like. The poles reverse. During the reversal and leading up to it you can get "mini-poles" that form in different spots and you can get weak spots in the magnetic field. The overall result might be slightly higher exposure to people living under weak spots.

[Rahvin]

Also expect major issues with migratory species that use the magnetic poles to navigate. Similarly, expect human navigation to have issues during any polar shift. If it's over quickly, we should be up and running without too terrible a hiccup, but if we go for months or years with the aforementioned "mini-poles" popping up, anything that relies on a compass will obviously be nigh-useless.

GPS should alleviate this for major shipping and air travel, though - or does GPS also rely on the magnetic poles for orientation data?

[Broomstick]

GPS is completely independent of the Earth's magnetic poles. Should the poles go wonky on us we'll just switch to GPS (or equivalent, as other nations/regions are developing their own satellite-based systems).

Commercial aviation and oceanic shipping phased out compass-based navigation many years ago, first with things like LORAN and then GPS (which can be set to either true or magnetic north). The problem with a major change in magnetic poles is that compass is still a backup to those other methods. So if the hi-tech primary navigation system fails the back up may be unreliable, too, if the magnetic field is doing odd things. That might result in a few more crashes/accidents than otherwise, but not many and possibly none.

The poles do move around anyway - the FAA regularly publishes data on changes in this. Originally, when I started learning to fly in 1995, my area was on the agonic line but our magnetic declination around here has changed over the years. Granted, only by a few degrees, but when flying even a single degree can quickly add up to a significant change in course over time and distance. The rate of these changes in magenetic declination does seem to be accelerating, but whether that's a sign of imminent reversal or just natural and normal cycles is anyone's guess.

A lot depends on just how fast a reversal takes place, how stable mini-poles are.... if reversals are quick, on a time scale of days or months, yes, compasses will be useless for a bit. If, however, it takes years - decades or centuries - then a compass may still have utility if you frequently update your declination information (perhaps as often as weekly or daily). As I keep saying, no one really knows as we have absolutely no historical information on pole reversals on a human timescale.

[Coyote]

Isn't the Sun going into some sort of highly-active cycle these days as well? Increased subspots, warmer, flares, etc? Could they be related?

[Samuel]

Isn't the Sun going into some sort of highly-active cycle these days as well? Increased subspots, warmer, flares, etc? Could they be related?

No. The Sun is on an 11 year cycle determined by its magnetic field. The Earth's magnetic field cycle is controlled by the Earth's core.

[Kanastrous]

Forgive the tangent, but why is it that the Earth has only two magnetic poles, but the sun has multiple ones? At least, that's what seemed to be the idea presented on a documentary I saw.

[starslayer]

A big wad of nothing happens to life on the surface. The Earth's atmosphere is great at stopping nasty things like cosmic rays. We may notice a small increase in the muon flux on the ground, but beyond that, nothing happens to endanger lives. Photons are unaffected by magnetic fields, and so nothing happens to them as things stand anyway.

Endangering our way of life, however, is another matter. The Earth's magnetic field plays a major role in keeping our satellite electronics working, and our astronauts alive. In fact, solar flares were a major concern on the Apollo missions; a single reasonably strong flare pointed our way would have killed anyone flying a mission to the Moon due to radiation sickness. If the Earth's field were to start undergoing a reversal, and the mini-poles showed up and persisted for several years, say, then the field would effectively "shrink" (technically what is happening is that the region over which the Earth's field has more influence than the Sun's shrinks). Depending on how much it shrank, various things could happen. Our satellites could be damaged and effectively knocked out due to the increased particle flux; during solar storms, radiation damage to satellites is a major concern, and a few tend to be destroyed (in the sense of permanently shut down) every strong solar flare. This means that the GPS system would be jeopardy because it depends on satellites. Another concern is for possible astronauts aboard the ISS or any other stations we may have. They would have to be brought back until the reversal was complete; the radiation danger would be too great otherwise.

If a coronal mass ejection (CME) were to occur during such a time, the effects could be catastrophic. Look up the geomagnetic storms of 1859 and 1989. In '89, almost the entire province of Quebec was left without power after a CME shorted out a transformer, and . In 1859, the CME was so strong that telegraph wires were destroyed, and some even caused fires, the induced current was so intense. If the 1859 storm were to happen today, with or without a reversal, power could be lost over much of the globe as the grids simply overload and the transformers that make it work are destroyed along with the transmission wires. The lights wouldn't be back on in most places for months or even years, as there are only a few places that make the heavy transformers for the grid, and they themselves would likely be without power.

Two more effects: as more particles hit the ionosphere, it heats up and expands. This causes drag on satellites in LEO, and a large flare can cause some of these to deorbit. All LEO satellites have periodic thruster burns to push them to higher orbits, counteracting present atmospheric drag. Also, any radio communications that depend on being bounced off the ionosphere are impossible for the duration of the storm.

Isn't the Sun going into some sort of highly-active cycle these days as well? Increased sunspots, warmer, flares, etc? Could they be related?

No, just the opposite in fact. It just came off solar minimum; this minimum was so low that either no or only one sunspot was seen for most of 2008. As Samuel said, the solar cycle is 11 years long, and solar maximum will be here in several years.

[Samuel]

Forgive the tangent, but why is it that the Earth has only two magnetic poles, but the sun has multiple ones? At least, that's what seemed to be the idea presented on a documentary I saw.

I had to do some searching just to check (I was positive, but I have been positively wrong), but no, the Sun has only 2 poles, just like the Earth. What you are thinking about is the magnetic field lines. They start to get messed up as the Suns surface is moving at different speeds, and you get more and more sunspots until the whole thing resets itself.

[CaptainChewbacca]

Sunspots cause more prominent variations in the sun's magnetic field than anything we have on earth, but its still only got the one magnetic field axis.

[Sky Captain]

I think Earth magnetic field helps to protect our atmosphere from being slowly blown away by solar wind. So in a long term (millions of years) lack of magnetic field could cause our atmosphere to become thinner and thinner. It`s theorized that Mars lost most of it`s atmosphere because it lacked strong magnetic field to keep solar wind out.

However in case of geomagnetic reversal period with weak magnetic field is too short to cause noticeable atmosphere depletion so this wont be a problem.

[Fleet Admiral JD]

Oddly enough, I was speaking to a professor I had for my natural science class last semester about this. He said we may see some increased mutations among life on Earth, as well as the aforementioned power outages, but it won't present a serious, direct danger to us besides a slightly increased risk of cancer.