audio for geodynamo

The theory of the geodynamo explains the constant shifting of the Earth's poles by suggesting that the rising and falling of hot and cool fluid in the outer core, along with the rotation of the Earth, creates electric currents that generate and maintain the magnetic field. The inner and outer core work against each other, with the outer core trying to reverse the field but being stopped by the solid inner core. This theory also explains why pole reversals can be random and far apart. The last reversal was around 780,000 years ago. This theory is still being researched and is the current best explanation. A simulation based on this theory shows the 3D magnetic field and how much the poles can vary before a full reversal. Theory. Magnetic signatures embedded in minerals at the Earth's surface indicate that the geomagnetic field has existed for at least 3 billion years. The poles are constantly shifting, and this suggests that something must be going on inside the Earth, continually degenerating the geomagnetic field, and this is where the theory of the geodynamo could explain. The theory goes that in the outer core of the Earth, the rising and falling of a hotter and cooler fluid, which is a convection current, due to the hot inner core heating up the bottom of the outer core, which each have their own magnetic field, paired with the way they get swirled around by the rotation of the Earth, creates these electric currents, which can all come together to induce another bigger magnetic field, while also reinforcing the original smaller ones. This keeps the magnetic field maintained. Sometimes, the poles can vary and even reverse, and this is about these convection currents being about unstable at times. The theory also shows the inner and outer core kind of working against each other, where the fluid in the outer core is continually trying to reverse the magnetic field, but the solid inner core is kind of stopping these reversals, because the field in the inner core can only change on a much longer timescale, so if it was just left up to the outer core, then really the poles would be reversing a lot more. And this could probably explain why the times between the reversals are so random, and some can be really far apart, and some can be really close together. Hence the fact that there have been nearly 200 pole switches in the last 100 million years, but the last one was around 780,000 years ago, so we are definitely over G1. This is also still an area of modern research, and so there's nothing to detriment really, it's just full theory. But it is the best we've got so far, so that's what we're sticking with. The figure shows a simulation of the 3D magnetic field based on the geodynamic theory. The magnetic field lines are blue where the fluid is directed inward, and yellow where directed outward. The rotation axis of the model earth is vertical and through the centre. There also seems to be a transition at the core-mantle boundary from the intense and complicated field structure in the fluid core, where the field is generated, to the smooth and potential field structure outside the core. It really is a crazy looking diagram, and it also shows how much the poles can vary before a full reversal in the cycle. Thank you.