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Session 120 - The Local Interstellar Medium.
Oral session, Thursday, January 18
Corte Real, Hilton

[120.03] Correlation Time Effects and Saturation of the Galactic Dynamo

B. D. G. Chandran, R. M. Kulsrud (Princeton University)

It has been argued (Kulsrud & Anderson, 1992) that turbulence in the interstellar medium cannot account for the large-scale magnetic field in our galaxy because small scale magnetic noise grows so quickly as to damp out the turbulence before a large scale field can grow. The argument, however, is based upon the assumption that the velocity correlation time is smaller than the growth time. This assumption is inaccurate for Kolmogorov turbulence. Through analytic and numerical investigations, we find that realistic correlation times reduce the growth rate of the magnetic noise, but only by a factor of 2. A separate calculation shows that once the energy in the small scale magnetic field becomes comparable with the energy in the turbulence, the turbulence becomes Alfvenic and stops amplifying the field. Turbulence in the ISM cannot, therefore, account for the galactic field.

Program listing for Thursday