Magnetic Storm (16 of 22)

Magnetic Storm

The last reversal was what, 780,000 years ago?
Before that, there was one about 200,000, before that, again actually less than 200, so in a sense we are a bit overdue for a reversal.
So is this why the field is getting weaker today?
Could it be getting ready to flip? Scientists needed to discover whether there was a link between changes in the strength of the magnetic field, and changes in its direction.
It was a very intriguing problem, something that was screaming out for an answer.
And computers were becoming powerful enough to actually solve a full set of equations that describe convection in the core of the Earth and how that motion generates a magnetic field.

In the 1990s, physicist Gary Glatzmaier decided to embark on a very ambitious experiment.
He put all the essential facts that scientists had learned about the Earth's molten core into a computer model: dozens of equations describing its dimensions, temperature, viscosity and so forth.
Then he let the model run to see how the magnetic field would evolve over hundreds of thousands of years of simulated time.
It's important to understand just how long these simulations take.
Each time the computer solves the equations it advances the whole solution one time step, and a time step is typically ten days.
And within ten days things don't change much, which means you have to do many, many solutions.
You have to solve it millions of times, tens of millions of times, in order to be able to simulate hundreds of thousands of years, which is what we needed.
One case may take six months of running on the fastest computers in the world.
I was using supercomputers from the Department of Energy, from NASA and the National Science Foundation, and no matter where I was, the first thing I'd do is make sure the computers didn't crash.
So it was something I did every day, seven days a week for over four years.
And I remember there was a period of time, I believe it was in the fall, and I was traveling to other universities and giving talks, and after a number of weeks I came back and decided, "Well, now I need to look at the details of the magnetic field."
And realized that it was in the reverse polarity! It really had reversed.