Drift measurements of theE-layer

Abstract

The drift of the E-layer diffraction pattern on the ground has been recorded at Kjeller (ϕ = 59° 58′ north, λ = 10° 06′ east) on 2 Mc/s during the period of June 1953 to September 1955. Three receiving points were put up and the amplitudes of the E-echoes were recorded (Mitra method). The time shifts between the maxima in the fading curves were recorded automatically by means of a Phillips recorder, or, optically on a three-beam oscillograph. The mean diurnal values of the east–west and north–south components of the drift in meters per second have been given for the seasons—winter, spring, summer, and autumn. The seasonal and annual curves have been analyzed and the mean values compared with the results from similar recordings at Cambridge, Washington, and Ottawa. There is a constant term indicating a prevailing drift towards southwest in winter and towards northeast in summer. There is a solar 12-hour term appearing during all seasons of the year. The mean annual values of phase and amplitude of this term at Kjeller are very similar to the corresponding term at Cambridge. The summer values have been analyzed for a lunar term, and a small but doubtful component has appeared. During daytime, there is no systematic change in the wind-directions on days with Es or normal E. At sunset, when the electron density of the normal E-layer is too low for reflecting the test frequency 2 Mc/s, there is a sudden change in the direction of the east–west component. The Es-layer recorded after sunset and during the night has a strong westerly component. On account of the width of the gate, it is not possible to decide if this is a height effect. Another explanation is that the diffraction pattern during night-time is not isotropic, but has a preferred orientation in north–south direction. This will simulate a strong increase in the east–west component of the drift. It is pointed out that the probability distribution along the north–south direction is systematically narrower than along the east–west direction. Examples of very narrow probability distribution in north–south direction at night are given. The conclusion to be drawn is that there seems to be a preferred orientation in north–south direction of the lines of maxima during daytime, which during night-time may appear as very predominant.