Magnetic field reversal

Question:
I want to know what would happen to the Earth if the magnetic poles were to change or become upside down?

Answer

In fact this has already happened a number of times in the Earth's history. The magnetic field of the planet has reversed with the magnetic north pole becoming the south pole and the magnetic south pole the north pole. Each reversal from one direction to the other taking about 1000 years.

The evidence for this comes from ancient lava rock samples. The field reversal has taken place maybe four times in the last four million years. The magnetic field remaining in one direction for long periods of a million years each with a reversal of a hundred thousand years or so in between. The average period between field reversal is about 250 000 years. However there are extremes. There is evidence that about 16 million years ago magnetic north shifted as much as 6 degrees per day! Reduces to about 15% in 10 000 years.

It is thought that the last field reversal was a little over three quarters of million years ago.

What would happen during this reversal.
(a) there would be a reduction of magnetic shielding during the change. This will allow potentially dangerous charged particles from the solar wind to fall on the planet.
(b) the Northern lights (aurora) would disappear.
(c) magnetic compasses would be useless for a while
(d) there would be an increase in cosmic ray flux – see (a)
(e) probable effects on the migration of birds who use the magnetic field by which to navigate.

The overall intensity of the Earth's magnetic field is decreasing and it is possible that it will reach zero by the year 4000 AD or even earlier. This began about 150 years ago and it has now decreased by about 12%. The magnetic poles are also drifting – the north magnetic pole is moving towards geographic north from the west.