The spatial energy spectrum of magnetic fields in our Galaxy
  Interstellar magnetic fields exist over a broad range of spatial scales, extending from the large Galactic scales ($\sim 10$ kpc) down to the very small dissipative scales ($\ll 1$ pc). In this paper, we use a set of 490 pulsars distributed over roughly one third of the Galactic disk out to a radius $R \simeq 10$ kpc (assuming $R_\odot = 8.5$ kpc) and combine their observed rotation and dispersion measures with their estimated distances to derive the spatial energy spectrum of the Galactic interstellar magnetic field over the scale range $0.5 - 15$ kpc. We obtain a nearly flat spectrum, with a 1D power-law index $\alpha=-0.37\pm0.10$ for $E_{\rm B}(k)=C k^{\alpha}$ and an rms field strength of approximately $6 \mu$G over the relevant scales. Our study complements the derivation of the magnetic energy spectrum over the scale range $0.03 - 100$ pc by \citet{ms96b}, showing that the magnetic spectrum becomes flatter at larger scales. This observational result is discussed in the framework of current theoretical and numerical models. 
J.L. Han (NAOC), K. Ferriere (Observatoire Midi-Pyr\'en\'ees, France),   R. N. Manchester (ATNF)