we can't coordinate basic health care communication on an emergency. Let's hope someone finds a way to place Advertising on those big magnets in case we came to need them.
If the magnetic field completely disappeared tomorrow the top layers of the atmosphere would start to be ionized and stripped away. There'd also be a slow change in the composition of the atmosphere due to neutron bombardment.
The process would only take a mere million years or so!
In the meantime the Earths atmosphere alone also blocks cosmic radiation to the extent that there's no immediate harm to life.
It's not often mentioned but these pole reversals aren't sudden/instantaneous across the planet. They can take a few thousand years to complete.
See: https://en.wikipedia.org/wiki/Geomagnetic_reversal
The most interesting part to me, from the Wikipedia page is:
> The magnetic field will not vanish completely, but many poles might form chaotically in different places during reversal, until it stabilizes again.