MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS
Abstract
Using 3D non-equilibrium ionization hydrodynamical simulation of the interstellar medium,
we study the electron density, ne, in the Galactic disc and compare it with the values derived
from dispersion measures (DMs) towards pulsars with known distances located up to 200 pc
on either side of the Galactic mid-plane.
The simulation results, consistent with observations, can be summarized as follows: (i) the
DMs in the simulated disc lie between the maximum and minimum observed values; (ii) the
log ne derived from lines of sight crossing the simulated disc follows a Gaussian distribution
centred at μ = −1.4 with a dispersion σ = 0.21; thus, the Galactic mid-plane ne = 0.04 ±
0.01 cm−3; (iii) the highest electron concentration bymass (up to 80 per cent) is in the thermally
unstable regime (200 < T < 10^{3.9} K); (iv) the volume occupation fraction of the warm ionized
medium is 4.9–6 per cent and (v) the electrons have a clumpy distribution along the lines of
sight.
