Tuesday, July 5, 2011

Dynamos in Physics Today

One of the standard jokes in astrophysical modeling is that if there is ever a discrepancy between your model and observations you simply attribute it to some combination magnetic fields and turbulence.  Let's say your model of star formation fails miserably to reproduce the observed initial mass function in our galaxy.  What do you do?  Blame turbulence and magnetic fields, present some overly simplistic explanation of why turbulence and magnetic fields would give you the right answer if you could just capture them properly, and then promise to include them in some ill-defined future simulation.

These two phenomena have a fundamental link  - dynamo action.  In the words of a very well-written article by two of the top researchers in the field of laboratory dynamos, Cary Forest and Daniel Lathrop, "[a]ll astrophysical plasmas are, as far as we know, magnetized and turbulent" and thus ripe for dynamo action.  The problem is that we are orders of magnitude removed in both simulations and experiments from some of the physical regimes where dynamo action takes place, even within our own solar system (see the graph on the right).

Check out the article over at Physics Today for a great explanation of why dynamos are so ubiquitous, why they are so hard to predict, and what is being done with theory, modeling, and laboratory experiments to unravel the mystery.

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