0.3''$ at 10 Mpc.

Figure \[fig:f1\] shows the result for a relatively simple case where the Faraday depth is virtually a monotonic function of physical distance. The top-left panel shows the distributions of thermal electron density and LOS ($z$ axis) component of magnetic fields in physical space along a LOS. As explained in the previous section, the density is concentrated near the galactic mid-plane within the scale height ($|z| \lesssim 1~{\rm kpc}$), while magnetic fields extend more to outer regions due to the halo magnetic fields. Both density and magnetic-field distributions have violent fluctuations caused by turbulence.

The resultant Faraday depth is shown as the blue dotted line in the bottom-left panel of Figure \[fig:f1\]. In this case, Faraday depth almost monotonically decreases with the physical distance because magnetic fields are mostly positive. The panel also shows the polarized intensity distribution, which shows that the intensity is peaked at the mid plane with tails in the halo. We find that variations of Faraday depth in halo ($|z| > 1~{\rm kpc}$) is small ($<1~{\rm rad/m^{2}}$), even though sub $\mu$G magnetic field extends to several kpc scale. This indicates the feature of Faraday caustics that polarized emissions in the halo tend to 