Spaced Receiver Technique Research Articles

A Method for Measurement of Drift in the Lower Ionosphere

ABSTRACTThis paper describes a method for determining the direction and speed of drift in the lower ionosphere. The spaced receiver technique originated by Mitra has been utilized for this purpose with the modification that the pulsed transmitter has been done away with. In this method C.W. signal from Radio Tashkent (164 kc/s.) has been received at Delhi on two receivers placed at a distance of 8 km. from each other. Properly oriented loop aerials of the Belrose type eliminated the ground wave from the received signal. The amplitude of the received signal was continuously recorded at the two receivers after appropriate synchronization. The fading patterns obtained on two charts were similar but showed a relative displacement along the time axis. Assuming one hop propagation it was possible to calculate the component of the ionospheric drift at the reflecting layer along the specified direction. This method can be a very useful one in determining the drift system in the lower ionosphere if a system of thr...

Horizontal drifts in the E-region at Waltair

Results obtained at Waltair on the measurement of ionospheric drifts for the E-region over a period of 2 years by spaced receiver technique are presented in this paper. The main features of the diurnal and seasonal variation of drifts in the E-region at this low latitude station are given in detail. These are compared with earlier results from other latitude stations as well as those obtained at this same station by previous investigators.

The heights of ionospheric irregularities in the auroral zone

Recordings of the 20 Mc/s signal strength of the satellite 1958 delta 2 were made. A spaced-receiver technique for measuring the heights of the irregularities responsible for the violent scintillations observed in these signals gives evidence that their altitudes ranged as high as 1000 km. A method for determining the height distribution of these irregularities, based on the amount of scintillation recorded when the satellite was at different altitudes, shows that they occurred mostly below 650 km and that occurrences at greater heights were sporadic.

A statistical study of ionospheric drifts measured by the radio star scintillation technique

Ionospheric drifts have been measured by the radio-star scintillation spaced receiver technique and histograms are presented showing the magnitudes and directions of the drifts observed. The direction of drift is commonly found to reverse suddenly near 2300 hours local time, but the complementary reversal occurs at a less definite time during the following day.

Horizontal drift in the ionosphere over Delhi

Some results obtained at Delhi on the measurement of ionospheric drift by spaced receiver technique are described. Most probable velocities of reflections from the F- and E-layers for different seasons are indicated by histograms. The diurnal variations of the magnitude and direction of the drift velocity have been plotted graphically. Harmonic analyses of the east-west and north-south components of the drift velocity have been worked out. No predominant periodicity in any of the components was observed. It is interesting to note that the most probable direction of the drift velocity is towards the south, and the northward component is almost completely inhibited. During magnetic storms, however, the northward component increases and its variation appears to be well correlated with the variation of the “ K” index.

Geomagnetic Field and Ionospheric Drift

Investigation of ionospheric drift by the well-known spaced receiver technique utilizing fading on pulsed transmission is in progress at the Research Department of All India Radio since January 1958 and forms a part of its programme of International Geophysical Year. There is some uncertainty as to the origin of this drift system at ionospheric heights. If the drifts were due to the effect of solar and lunar gravitational tides upon a uniformly rotating sphere, one would expect the drift vector to exhibit a predominant semi-diurnal periodicity. Experimental observation indicates that this is not always the case. In fact there is hardly any regular behaviour in diurnal variation of the phase of the drift system. One would, therefore, like to enquire whether earth's magnetic field exercises any influence on the drift system and is responsible for irregular variation of its phase. It is likely that such an influence should exist as the ionosphere consists of charged particles. We have correlated the magnetic K index (Alibag figures) with the magnitude of the drift velocity with a view to finding out any interdependence. The analysis shows that so far as the magnitude of the drift velocity is concerned, it is fairly independent of the variation in the values of K; in fact large magnetic storms have failed to produce any significant change in the magnitude of the drift velocity. The variation of east-west and north-south components of the drift velocity during a ‘quiet’ day does not indicate any correlation with K; but on ‘disturbed’ days, the northward velocity of the north-south component increases in synchronism with increase in K.

73. Orbits of sporadic meteors

A survey of sporadic meteor orbits has been made using a spaced receiver technique. The apparatus consists of three receivers spaced on the ground by about 4 km. The received signals are brought together by radio links and displayed on a single film. In this way both diffraction pattern and the time delay between the diffraction patterns received at the different stations can be measured. From this the velocity and the direction of motion of the meteor can be calculated. The range of the echo and the local sidereal time are also recorded on the film.