2011MNRAS.416.1152J

We extend previous work modelling the Galactic magnetic field in the plane using synchrotron emission in total and polarized intensity. In this work, we include a more realistic treatment of the cosmic ray electrons using the GALPROP propagation code optimized to match the existing high-energy data. This addition reduces the degeneracies in our previous analysis and when combined with an additional observed synchrotron frequency allows us to study the low-energy end of the cosmic ray electron spectrum in a way that has not previously been done. For a pure diffusion propagation, we find a low-energy injection spectrum slightly harder than generally assumed: for J(E) ∝E^α, we find α=-1.34±0.12, implying a very sharp break with the spectrum above a few GeV. This then predicts a synchrotron brightness temperature spectral index, β, on the Galactic plane, that is -2.8 < β < -2.74 below a few GHz and -2.98 < β < -2.91 up to 23 GHz. We find that models including cosmic ray re-acceleration processes appear to be incompatible with the synchrotron data.