Solar radio-frequency reflectivity and localization of FRB from solar reflection

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 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 low frequencies (⪅ 100 MHz) and grazing incidence (angles ⪆60^◦), but exceeds 0.1 for frequencies ⪅ 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.