Institute for Advanced Study Astrophysics Seminar

ABSTRACT: Large scale magnetic fields are found everywhere in the universe, from the scales of planets to galactic disks (or larger). Understanding their generation and maintenance has proven to be unexpectedly difficult. I will discuss topological constraints on the growth of such fields, and argue that they are inconsistent with kinematic dynamo theory. Instead, I propose a modified version of mean field dynamo theory in which field growth is not exponential, but can grow from infinitestimal seeds in a very short time. I compare the predictions of the model to observations of stellar magnetic fields.