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D. Balsara (Univ. of Notre Dame)
Several lines of evidence suggest that magnetic fields grow rapidly in protogalactic and galactic environments. We show that an interstellar medium that is dominated by realistic energy input from supernova explosions will naturally become a strongly turbulent medium with large positive and negative values of the kinetic helicity. The turbulent flow that we model has fast magnetic energy growth independent of scale, and with a growth time that is comparable to the eddy turn-over time. Energetics, power spectra, statistics and structures of the turbulent flow are studied here. Various indices of Lagrangian chaos are studied in the resulting flow. The line stretching rate in these flows is studied and found to be exponentially fast. Liapunov exponents are also studied and are shown to relate to the growth of field. The resulting flows are shown to have constructive folding that is substantially lower than the optimal rate but still sufficient to drive a fast dynamo. Shock-turbulence interaction is shown to be a very general mechanism for helicity generation and magnetic field amplification with applicability to damped Ly-alpha systems, protogalaxies, the Galaxy, starburst galaxies, the inter-cluster medium and molecular clouds. Support via NSF grants R36643-7390002, AST-005569-001 and DMS-0204640 is acknowledged.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.