Production and decay of magnetic fields in relativistic turbulence

Given that many diverse astrophysical systems are susceptible to relativistic hydromagnetic turbulence, it is surprising how little is presently known about how they manifest chaotic flow. Of primary interest is to establish a basic understanding of how the small-scale turbulent dynamo, whereby kinetic energy of the flow is converted into magnetic energy, operates in these systems. This process is thought to be instrumental in both stellar and galactic magnetogenesis, and may also be at work in relativistic astrophysical jets and their central engines.

Of equal importance is to understand how magnetic energy decays in the absence of continued stirring by external forces. For example, if magnetic fluctuations are driven locally (in a pulsar magnetosphere for instance) what fraction of the Poynting flux survives to infinity, and how much is trapped by collisions with ambient Alfven waves? Similarly, can turbulent magnetic fields produced by plasma instabilities upstream of a relativistic blast-wave survive long enough into the downstream to be consistent with synchrotron models for GRB afterglow emission?

I will present results from large-scale numerical simulations which are providing answers to some of these questions, and discuss ongoing efforts to answer others. If there is time, I will also explain how simulations of relativistic turbulence can be used to synthesize images of polarized synchrotron emission from giant radio lobes, thereby assessing the possibility that they are in a state of turbulence.