Radio Emission of Auroras at a Frequency of 3000 MHz

On the night of January 24–25, 1949, in the city of Saskatoon (Canada), an aurora was observed that was unusual in magnitude and variety of forms (a red glow of the sky was seen even in California and British Columbia).¹ At first it appeared as a reddish glow of the sky; then a beautiful corona appeared, green at the zenith and passing into red layers at the eastern and western edges. Somewhat later, three bright homogeneous arcs were observed. During the night one form of aurora was replaced by another, and among them there were forms of both ray structure and non-ray structure. Similar phenomena were also observed on the night of February 21–22.

A photograph of the solar surface taken at noon on January 24 showed the presence of an enormous group of sunspots. This group of spots was also present on February 21, although it had significantly smaller dimensions.

Short pulses of radio emission originating from the region of the aurora were first detected on January 24 by a radar installation operating at a wavelength of 10 cm.³ Subsequent observations at a wavelength of 10 cm also revealed radio emission caused by the aurora.

For the observations a radar receiver was used, equipped with an additional device that recorded the frequency of occurrence of the received pulses. A film camera was mounted on the antenna, which received radiation from a solid angle of \(6.3 \cdot 10^{-3}\) steradian, so that the observer could photograph the portion of the sky at which the antenna was directed.

The observations carried out show that the radio emission of the aurora has a pulsed character, with the duration of individual pulses being on the order of 1–5 microseconds. The magnitude and frequency of occurrence of the pulses vary within wide limits and apparently depend on the brightness and structure of the aurora. Thus, auroras of ray structure are more active with respect to radio emission than auroras of non-ray structure.

Observations of the radio emission of auroras, as the authors of the note point out, are continuing with the aim of establishing the quantitative dependence of the intensity and character of the radio emission on the type and intensity of the aurora, and also with the aim of clarifying the mechanism by which the radio emission arises.

G. Getmantsev

References

1. W. Petrie, P. A. Forsyth, E. M. Conencky, Nature 163, 774 (1949).
2. P. A. Forsyth, W. Petrie, B. W. Currie, Nature 164, 453 (1949).