Our poles are supposed to switch north and south semi-regularly, over long periods of time.
Question 1 - how long are these periods?
2 - does it switch all at once, or ‘fade out’ and then switch over?
2a - if it does fade out, how long does that process take?
lots of species use magnetic north or south to navigate or to migrate.
1 - what is expected to happen to species that use magnetic north (or south) to migrate? To navigate?
2 - Are there records of species die-offs attributable to this?
3 - is there any way to mitigate this for important or well-loved species?
if the magnetosphere is down for any length of time, we’re getting pounded with solar radiation.
1 - are our electronic devices and networks shielded well enough to withstand that sort of thing nowadays? I recall stories of a bad solar storm in the 1800s? causing telegraph offices? to go up in flames.
2 - what sort of cumulative cancer/mutation damage is that going to cause to people/animals?
The magnetic shift is pretty random, with periods anywhere between 0.1 and 1 million years being the most common.
We don’t know exactly how long it takes, since we’ve never witnessed one. Current estimates are that the transition takes somewhere between 1,000 and 10,000 years to complete, but there is some evidence (taken from lava flows) that it could change by as much as 6 degrees per day. This seems to indicate more of a slow shift rather than a fade out and fade in. However, others theorize that the field could disappear or be greatly weakened during the shift. Or maybe it just gets erratic. There’s a lot of conjecture at this point.
Most species don’t rely solely on magnetic fields for navigation. However, possible extinctions have been theorized, not only due to loss of navigation but also due to increased bombardment of solar particles that are currently deflected by the magnetic field.
Consumer electronics are not well shielded.
All of the numbers above were taken from the wikipedia page for geomagnetic reversal:
“Every so often—every 250,000 years on average—the Earth’s magnetic poles reverse polarity. If such a reversal happened today, compass needles would point south rather than north. Here, view a computer-model-generated animation of our planet’s magnetic field, and see what happens during a reversal.”
We’ve never seen the Earth reverse field, but we have seen the Sun do it, and that gives some guidance on the matter. When the Sun reverses (every 11 years, on a fairly regular schedule), it’s not a matter of the poles moving, nor does the field disappear entirely. Rather, the field becomes a messy tangle with poles all over the place, and then the extra poles merge again and untangle into the opposite dipole configuration.
It’s not a perfect analogy: Field reversals in the Earth are a lot messier, mostly due to the conductive fluid responsible for the magneto being a lot more viscous and more resistive. But the broad picture is probably the same.
Scientific American had a nice, one-page summary in its October issue, Earth’s Impending Magnetic Flip. Basically it says what engineer already said.
The last reversal was 780,000 years ago. The field is weakening and could begin reversing in less than 2000 years. Sometimes, though, the trigger just peters out, and several false starts are known. If it does flip, everybody will have a lot of time to adjust: the flipping takes an average of 5000 years with extremes of 1000-20000. No mass extinctions or increased radiation damage are associated with past reversals.
In short, it’s such a far future event that we can’t say anything about the effects because everything will have changed drastically by then.