The Association of Radio Fade-Outs with Solar Eruptions
Abstract
Since the announcement in 1936 that radio fade-outs were coincident in time with solar eruptions, a large number of observations have confirmed this beyond all doubt, but whether a particular eruption will be accompanied by a fade-out has not, hitherto, received much consideration. This question is examined in detail in the following discussion.Observations of fade-outs at the Commonwealth Solar Observatory, Canberra, Australia, have been made since June 1937 with automatic P‧ - f (multifrequency) equipment. Briefly, this consists of a pulse-transmitter, the frequency of which is automatically varied over a range from 2.3 to 12 mc/sec, and a special receiver, automatically tuned to the frequency of the transmitter. The complete cycle of operations is repeated, in the present instrument, every six minutes, while in the first instrument, which was in use until April 1938, the period was made five or fifteen minutes according to the solar activity. The signals picked up by the receiver are delineated, finally, on the screen of a cathode-ray oscillograph where the “ground-wave” and reflections, or “echoes,” from the E- and F-regions of the ionosphere are separated. The resulting quasi-stationary picture is photographed on a moving film. For the purposes of this paper a fade-out is defined as a period during which no reflections from the E-region can be seen; a “severe” fade-out is one in which, in addition, no echoes from the F-region are visible, while a “minor” fade-out is one in which some F-region echoes, though weakened, are present. It should be emphasized that this criterion for a fade-out is not absolute and refers particularly to the special transmitter and receiver used in the investigation, though it is worth pointing out that such fade-outs observed here invariably coincide with periods of severe disturbance to commercial radio services.
- Publication:
-
Terrestrial Magnetism and Atmospheric Electricity
- Pub Date:
- 1939
- DOI:
- 10.1029/TE044i002p00181
- Bibcode:
- 1939TeMAE..44..181G