Density Distribution of the Warm Ionized Medium

Observations of Hα emission measures and pulsar dispersion measures at high Galactic latitude (|b| > 10◦) provide information about the density and distribution of the diffuse warm ionized medium (WIM). The diffuse WIM has a lognormal distribution of EMsin |b|, which is consistent with a density structure established by isothermal turbulence. The H responsible for most of the emission along high-EMsin |b| sightlines is clumped in high density (> 0.1 cm) regions that occupy only a few parsecs along the line of sight, while the H along low-EM sightlines occupies hundreds of parsecs with considerably lower densities.