Loops and spurs: The angular power spectrum of the Galactic synchrotron
  background
  We present a new model of the diffuse Galactic synchrotron radiation,
concentrating on its angular anisotropies. While previous studies have focussed
on either the variation of the emissivity on large (kpc) scales, or on
fluctuations due to MHD turbulence in the interstellar medium, we unify these
approaches to match the angular power spectrum. We note that the usual
turbulence cascade calculation ignores spatial correlations at the injection
scale due to compression of the interstellar medium by old supernova remnants
-- the 'radio loops', only four of which are visible by eye in radio maps. This
new component naturally provides the otherwise missing power on intermediate
and small scales in the all-sky map at 408 MHz. Our model can enable more
reliable subtraction of the synchrotron foreground for studies of CMB
anisotropies (both in temperature and polarisation) or searches for dark matter
annihilation. We conclude with some remarks on the relevance to modelling of
the polarised foreground.
