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Magnetic Dipole Emission from Magnetic Grain Materials

If interstellar grains contain magnetic materials, thermal fluctuations in the magnetization will result in magnetic dipole emission (Draine & Lazarian 1999a). The predicted emission is shown in Figure 1 for various assumptions: 100% of the Fe in paramagnetic amorphous silicate mineral; 100% of the Fe locked up in magnetite (Fe3O4); or 5% of the Fe present in small metallic iron particles, either bare ellipsoids or inclusions within silicate grains.

Also shown are observational data points for microwave emission correlated with 100$\mu$m thermal emission from interstellar dust, in terms of microwave emissivity per H nucleon (see Draine & Lazarian 1999a,b).

Figure 1: Emissivity per H atom due to magnetic dipole emission from possible magnetic grain materials, plus the low-frequency tail of the ``vibrational emission'' from the overall grain population, for an assumed emissivity $Q_\nu\propto\nu^{1.7}$. See Draine & Lazarian (1999b)  
\epsfig {file=/u/draine/papers/3Kconf/f3.eps,height=4in,width=4in}


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Bruce Draine