Astrophysical fluid dynamics

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Magnetic fields are found almost everywhere in the universe, and play a vital role in the creation of high energy particles, the accretion of gas onto black holes, and the formation of stars. Nevertheless there is considerable controversy regarding their origins and an equal amount of uncertainty with regard to their behavior, which in turn implies a great deal of uncertainty in our understanding of a wide variety of astrophysical phenomena. There is general agreement that the origin and evolution of magnetic fields are closely tied to the turbulent motions of gas in the interstellar medium and inside stars. Here we propose to study several key processes connected to magnetic fields and star formation. One of these is the general process of magnetic field formation (i.e. dynamo activity) in conducting fluids, which means almost all hot gases including stars, accretion disks and the interstellar medium. This is directly connected to the origin of galactic magnetic fields and in particular the question of whether or not strong and well organized fields arise quickly once galaxies form, as observations indicate, or whether we must appeal to exotic physical processes in the early universe to understand the evolution of galactic magnetic fields. Second, if we visualize magnetic fields as composed of "field lines" then a commonly noted paradox is that these field lines appear to "reconnect", or switch attachments, without much difficulty both inside and outside of stars. Although there has been a great deal of work on undrstanding magnetic reconnection in low density environments, like the interstellar medium, this work does not help us understand magnetic reconnection inside stars. I have been studying the effects of turbulence on this process and will conduct a series of numerical experiments to test previously published ideas on fast magnetic reconnection in turbulent fluids. Third, I will apply the work on dynamos and reconnection to the generation and transport of magnetic fields in disks, which are critical for quasars and star formation. Finally, I will examine the interplay between magnetic fields and fluid instabilities in the early stages of star formation.