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

TL;DR

This paper models the Sun's radio-frequency reflectivity to assess its potential for localizing Fast Radio Bursts via solar reflection, complementing previous lunar reflection studies.

Contribution

It introduces a calculation of the Sun's radio reflectivity as a function of angle and frequency, expanding the understanding of FRB reflection sources beyond the Moon.

Findings

Reflectivity is high at frequencies below 100 MHz and grazing angles.

Solar corona emission likely prevents detection of solar reflections of FRBs.

Solar reflection can narrow down FRB source locations when combined with lunar reflections.

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.