Interplanetary Type III Radio Emission Locations Deduced from the Underlying Electron Exciter Beam Kinematics

Abstract Direction-finding techniques from spacecraft have been used to locate and track interplanetary type III radio sources for many decades. These source locations are typically found to be farther from the Sun than expected on the bases of interplanetary density profiles derived from white-light and in situ observations. This puzzling result has led to suggestions that interplanetary scattering and other propagation effects may play an important role in shifting the observed locations of the radio sources away from the intrinsic or true radio emission regions. It is only recently that it has been possible to quantify the effects of anisotropic scattering on the locations of the individual type III radio sources in the solar corona and interplanetary medium. However, it is challenging to confirm these interplanetary scattering predictions with observations since the intrinsic radio emission regions in the interplanetary medium cannot easily be directly identified. We use the electron exciter beam kinematics, deduced from the remote and in situ radio observations, as a diagnostic of the intrinsic type III radio emission regions to compare with the observed type III source locations derived from two-spacecraft triangulations and to the expectations from isotropic and anisotropic scattering models. Our analyses suggest that the locations of the interplanetary type III radio emission regions are not significantly displaced, either radially or longitudinally, from the two-spacecraft triangulated source locations.