Evidence for halo-like radio sources from kilometric type III burst observations

The radio azimuths for many kilometric type III bursts that originate near or behind the limb of the Sun are observed to drift far to the east or far to the west of the spacecraft-Sun line. It is shown that the behavior of the observed burst parameters for these events corresponds to the response of a spinning dipole antenna to halo-like sources of radiation around the Sun. Our results provide evidence for a previous suggestion that behind-the-limb type III events should appear as halo-like sources of radiation to an observer on the opposite side of the Sun, due to scattering of the radiation from the primary source back around the Sun.