  Recently, Sun et al. (2008) published new Galactic 3D-models of magnetic
fields in the disk and halo of the Milky Way and the distribution of cosmic-ray
electron density by taking into account the thermal electron density model
NE2001 by Cordes & Lazio (2002, 2003). The models successfully reproduce
observed continuum and polarization all-sky maps and the distribution of
rotation measures of extragalactic sources across the sky. However, the model
parameters obtained for the Galactic halo, although reproducing the
observations, seem physically unreasonable: the magnetic field needs to be
significantly stronger in the Galactic halo than in the plane and the
cosmic-ray distribution must be truncated at about 1 kpc to avoid excessive
synchrotron emission from the halo. The reason for these unrealistic parameters
was the low scale-height of the warm thermal gas of about 1 kpc adapted in the
NE2001 model. However, this scale-height seemed well settled by numerous
investigations. Recently, the scale-height of the warm gas in the Galaxy was
revised by Gaensler et al. (2008) to about 1.8 kpc, by showing that the 1 kpc
scale-height results from a systematic bias in the analysis of pulsar data.
This implies a higher thermal electron density in the Galactic halo, which in
turn reduces the halo magnetic field strength to account for the observed
rotation measures of extragalactic sources. We slightly modified the NE2001
model for the new scale-height and revised the Sun et al. (2008) model
parameters accordingly: the strength of the regular halo magnetic field is now
2 microG or lower, and the physically unrealistic cutoff in z for the
cosmic-ray electron density is removed. The simulations based on the revised
3D-models reproduce all-sky observations as before.
