A geomagnetic reversal is a change in a planet’s magnetic field such that the positions of magnetic north and magnetic south are interchanged. This happened briefly on Earth some 41000 years ago, but apart from this the current magnetic arrangement has been intact for 780,000 years. Before that time, geomagnetic reversals have happened on average every 300,000 years, with no clear patter.
The irregularity and long time spans between pole reversals on Earth is in stark contrast to our Sun which sees a pole reversal every 11 years, synchronized neatly with the solar cycle. Interestingly, there is no visible change in the Sun’s surface features corresponding to its pole shifts. Yet we know that changes in magnetic fields are always associated with changes in electric currents.
The electric currents associated with astronomic bodies are interstellar Birkeland currents, so it’s reasonable to assume that pole reversals are due to reversals in these currents. With the Sun at the center of our local interstellar Birkeland current, it is the body most affected by it. The situation on Earth is more like a turbulence in the outskirts.
If this is how things hang together, we should be able to see a change related to the Sun. Its chromosphere and corona should display a reversal in their overall twist. Correspondingly, a geomagnetic reversal on Earth is likely to be associated with a change in weather patterns. The jet stream is likely to reverse. Ocean currents may also be affected. The Scandinavian Ice Sheet which is currently kept down due to the Gulf Stream and persistent mild air flows from the Atlantic may suddenly come back.
A possible reason for the stability of Earth’s magnetic field relative to the Sun is that our jet stream is powered in part by the rotation of our planet, as suggested by Dr. Gerald Pollack. A reversal in the Birkeland current may not always be enough to turn the jet stream around. It may merely weaken the jet stream without reversing it. With the jet stream continuing in its current direction, the direction of Earth’s magnetic field will remain as it is.
However, should the local Birkeland current manage to reverse Earth’s jet stream, a geomagnetic reversal would follow. But the strength of the magnetic field will not be as strong, and the jet stream will be weak. This is because the rotation of our planet will continue largely unaffected. Earth’s own contribution to the jet stream will always be in the direction of its rotation, no matter which way the Birkeland current twists. The jet stream is therefore always at its strongest when the Birkeland current twists in the same direction as our our planet is rotating, and at its weakest when the two factors are in opposition to each other.
But the rotation speed of Earth is not completely independent of the Birkeland current. When the current twists in opposition to Earth’s rotation, Earth slows down by a tiny bit. When the current is in tune with Earth’s rotation, Earth speeds up. Since our local Birkeland current appears to correspond to the sunspot cycle, we should see changes in Earth’s rotation speeds corresponding to this. This has been partially confirmed. Earth slows down and speeds up in its rotation in cycles of about 25 years, roughly twice the period of a solar cycle.
Interestingly, volcanic activity always sees an uptick during Earth’s periodic slow downs. A pole reversal, which would be associated with a relatively strong slow down, is therefore likely to come with much volcanic activity.
A pole reversal would also come with a dramatically weaker jet stream, with much instability in our weather patters as a consequence, making it harder to grow crops. Not only will we see a need to move food production due to changes in the climate, the production will be hampered by instability. Considerable hardships can therefore be expected if a geomagnetic reversal was to happen.
An alternative possibility to the geomagnetic reversal laid out above is that Earth itself has flipped over on occasions. This may sound impossible. However, the Tippe-Top theory first proposed by Peter Warlow outlines a simple mechanism for such an event to have happened.