Prompt and delayed Radio Bangs at Kilohertz by SN 1987A: A test for graviton-photon conversion

A sequence of prompt and delayed radio signals at tens of kilohertz should reach the Earth (or Jupiter) due to graviton--photon conversion in interstellar as well as local planetary magnetic fields. These radio fluxes may be a detectable probe of a huge gravitational burst expected from Supernovae explosions. The earliest prompt radio signal, coinciding with the neutrino burst, is due to conversion in the terrestrial (or Jovian) magnetic field and is below the micro-Jansky (or milli-Jansky) level for a galactic Supernova like SN1987A. A later radio signal, a ``tail'', due to the same graviton - radio wave conversion in random interstellar fields will maintain a relic radio ``noise'' for hundreds or thousands of years and might even be still detectable by a very sensitive network of satellite antennas at the kilohertz band. Exact solutions are presented here for the graviton-photon conversion in a refractive medium, as well as their consequences for high energy supernovae and the 2.726 K background radiation.