Spectra of the non-thermal radio radiation from the galactic polar regions

Measurements of the galactic radio background radiation have been made at 5.2, 9.0, 15.6 and 23.0 MHz using half-wave dipoles directed towards declinations $$\delta = 49^{\circ} \,\text{and} \,\delta = -43^{\circ}.$$ The same receiving equipment and calibration standard was used for both sets of measurements, and the temperatures of the regions closest to the galactic poles for these declinations were found to agree within 10 per cent. The data are compatible with the recent RAE-2 satellite spectra and the southern measurements of the Sydney group. A straight spectrum from 6 to 100 MHz gives a total background spectral index of 0.55 ± 0.03. The observed polar spectra can be explained by a simple model consisting of a disk of uniform emission and absorption, and an extragalactic component which is responsible for about 18 per cent of the total emission at 10 MHz.