Parsec-scale structure in galactic disk and halo, from diffuse radio polarization

We present multi-frequency polarization observations of the diffuse radio synchrotron background modulated by Faraday rotation. No total intensity is observed, indicating that total intensity does not vary on scales below approximately a degree. However, polarized intensity and polarization angle show abundant small-scale structure due to Faraday rotation in the warm ionized disk on small scales. The distribution of Rotation Measures enables us to estimate structure in magnetic field, weighted with electron density, in the warm ionized disk.