Measured solar radio flux spectra for quiet conditions and during solar storm (burst) events (the flux for Jovian bursts and the supernova remnant Cassiopeia A is shown additionally) (after Boischot, A., Solar radio astronomy, in Solar Physics, edited by J.N. Xanthakis, pp. 465-481, Wiley Interscience, 1967; Copyright John Wiley and Sons, reproduced with permission).