AAS 195th Meeting, January 2000
Session 51. ISM: Theory and Modelling
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[51.06] The Dissipation of Turbulence as a Heat Source in the Warm Ionized Medium

J. M. Wilson (U. Washington), D. S. Balser, A. H. Minter (NRAO)

The observed properties of the diffuse warm ionized gas (WIM) in our Galaxy are not consistent with photoionization models. Photoionization models, however, can reproduce the observed properties in classical HII regions. For some time now there has been mounting evidence of an additional heating source in the WIM. This conclusion is based on the fact that the recombination lines, which are produced almost entirely by the stellar radiation field, are consistent with the models but the fine structure lines, excited primarily by collisions, are more intense than the predictions from photoioniztion models. Recent observations of the WIM suggest that any additional heating source must supply heat with a rate per unit volume proportional to a lower power of the electron density than the heating rate (Reynolds et al. 1999, ApJ, submitted).

A promising candidate is the dissipation of turbulence which heats the interstellar medium in our Galaxy at a rate which is approximately proportional to the density. Models which include both photoionization and heating from turbulence have had some success (Minter & Balser 1997, ApJ, 484, L133). Here we expand on these initial models using the numerical program CLOUDY (Ferland 1996). We explore a variety of physical conditions with over 10,000 different models. Models which include turbulent heating fit the observations much better than models without extra heating for a large range of the physical conditions explored (e.g., electron density, filling factor, radiation field).

This work was funded by the National Science Foundation's Research Experiences for Undergraduates program.

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