Directional Observations of Radio Noise from the Outer Atmosphere

Abstract

ALTHOUGH many observations have been made in the past of the spectra of the radio emissions of the Earth's outer atmosphere in the frequency band 2–40 Kc./s.^1,2, it is only recently that a technique has been developed for continuously monitoring the occurrence of these phenomena³. This has revealed that radio noise bursts lasting some hours are normally associated with disturbances of the geomagnetic field and follow many high-frequency radio outbursts from the sun. It seems likely that these very low frequency noise bursts are caused by the interaction between auroral streams of charged particles and the plasma of the outer atmosphere, and proposed mechanisms include Cerenkov radiation^4,5 and gyro- or synchrotron radiation². Studies of their spectra, however, have not provided any clear-cut tests of these theories and it appears that additional information is required.