Solar Radio-Frequency Reflectivity and Localization of FRB from Solar Reflection

Abstract: The radiation of a Fast Radio Burst (FRB) reflects from the Moon and Sun. If a reflection is detected, the time interval between the direct and reflected signals constrains the source to a narrow arc on the sky. If both Lunar and Solar reflections are detected these two arcs intersect, narrowly confining the source location on the sky. A previous paper calculated reflection by the Moon. Here we calculate the reflectivity of the Sun in the "flat Sun" approximation as a function of angle of incidence and frequency. The reflectivity is high at frequencies $\lessapprox 100\,$MHz and grazing incidence (angles $\gtrapprox 60^\circ$), but exceeds 0.1 for frequencies $\lessapprox 80\,$MHz at all angles. However, the intense thermal emission of the Solar corona likely precludes detection of the Solar reflection of even MJy Galactic bursts like FRB 200428.