Keith Moffatt - Stars, Planets and Galaxies?

Keith Moffat, Emeritus Professor of Mathematical Physics at the University of Cambridge, addresses magnetic field generation.

About Keith Moffatt

"I’m Emeritus Professor of Mathematical Physics at the University of Cambridge and a Fellow of Trinity College, Cambridge.

My research field is fluid mechanics in all its aspects, ranging from the micro scale, applicable to biological fluid mechanics in particular, to the macro scale interaction with magnetic fields, with relevance to planets, stars and galaxies."

A complex interaction

My own involvement in astrophysics started when I was a PhD student. My thesis topic was the interaction of turbulence with magnetic fields. That involves both the Navier–Stokes equations and Maxwell’s equations for the electromagnetic field, and the very strong interaction between these topics in electrically conducting fluids. When you have currents flowing in these fluids, magnetic fields result, and the interaction of currents and magnetic fields affect the fluid motion. So, it becomes a very complex interaction. My own involvement has been primarily in the field known as dynamo theory, explaining the origin of magnetic fields and the way they evolve in planets, stars and even galaxies.

Key Points

• My thesis topic was the interaction of turbulence with magnetic fields. That involves both the Navier–Stokes equations and Maxwell’s equations for the electromagnetic field, and the very strong interaction between these topics in electrically conducting fluids.
• A bootstrap effect, or a magnetic instability, gives rise to the generation of the magnetic field of the Earth.
• Without the magnetic field of the Earth, we would be subject to extremely harmful radiation. It’s doubtful whether any of us could survive that radiation.