Volume Filling Factors of the DIG

Combining dispersion measures, distances and emission measures for 157 pulsars lying above \mid b \mid > 5 degree and between 60 degree < l < 360 degree we find the mean volume filling factor (\bar{f_v}) of the diffused ionized gas in the Milky Way. This filling factor is inversely related to the mean electron density (\bar{n_c}) in the clouds, \bar{f_v} = (0.0184 +/- 0.0014) \bar{n_c}^{-1.07 +/- 0.03}, implying a nearly constant average electron density distribution within 3 kpc of the sun.