Journey to the Core

An Internet guide to the planets' magnetic fields

Nevertheless, the virtual core is already a reality. In 1995, geophysicists, Gary Glatzmaier, now at the University of California in Santa Cruz, and Paul Roberts, at the University of California, Los Angeles, had created the first successful model of a self-sustaining magnetic field—one that even flipped polarity spontaneously after a 36,000-year run. Go to the PBS NOVA program site “Magnetic Storm” ( and click “See a Reversal” in the box to the right. There you will find slideshow with movies that show the model’s evolving magnetic field as it switches. At the Pittsburgh Supercomputing Center page When North Goes South, Glatzmaier and Roberts’s model is displayed in all its complexity, complete with 3D animations of twisting magnetic field lines. Japanese researchers are also modeling the core with supercomputers. Go the image gallery at the Earth Simulator Center at the Yokohama Institute for Earth Sciences, and scroll down to the “Simulation Results: Movie” and select the last image. The movie will show you a virtual reality system that takes researchers into the 3D space of the core to get a better feel for its magnetic twists and turns. There is little English explanation, but Disney would have loved it.

The core of the planet, shrouded by the mantle and crust, has given up its secrets slowly for the simple reason that it cannot be studied directly. But what if we could go to the core? Before moving on to magnetic fields on other planets, I recommend deep-cave explorer Bill Stone’s Technology, Entertainment, Design (TED) lecture entitled “Journey to the Center of the Earth” in which he proposes to do just that. Make of his proposal what you will, but it certainly gets you thinking about the difficulties.

Other planets—and stars—generate magnetic fields, but not all. For a quick comparison of magnetic fields throughout the Solar System return to David P. Stern’s site. For a somewhat technical look at the work being done by Glatzmaier and his collaborators on the fields emanating from Saturn and the Sun go to their page at the University of California Santa Cruz. Magnetic fields turn out to be key to understanding the interiors of all worlds, not just our own.

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