XXIX. On the nature of the discrete radio sources

The theory that the galactic radio noise emitted by the discrete sources is due to the interaction of a local magnetic field and cosmic ray electrons is tested quantitatively for the source in Cassiopeia. It is shown that the average magnetic field must be of the order of 0·01 gauss, which is approaching the upper limit imposed by energy considerations. At frequencies below 15 Mc/sec resonant reabsorption of the r.f. energy becomes important and if the theory is valid the r.f. power received at the earth should vary at least as rapidly as v 5/2 below a critical frequency in the range 10–20 Mc/sec.