Connecting synchrotron, cosmic rays and magnetic fields in the plane of the Galaxy

T. R. Jaffe, A. J. Banday, J. P. Leahy, S. Leach, A. W. Strong

    Research output: Contribution to journalArticlepeer-review


    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) ∝Eα, 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. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.
    Original languageEnglish
    Pages (from-to)1152-1162
    Number of pages10
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number2
    Publication statusPublished - Sept 2011


    • Cosmic rays
    • Galaxy: structure
    • ISM: magnetic fields
    • Polarization
    • Radiation mechanisms: general
    • Radio continuum: ISM


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