Computer simulation of ionospheric radio drift measurements, and their analysis by correlation methods

Abstract

A computer model is used to simulate spaced‐antenna ionospheric drift experiments. It is shown that the random or “characteristic” velocity Vc observed by correlation analysis is about equal to the root‐mean‐square deviation of the velocity distributions used in the model. Correlation analysis with four fixed antennas is also shown to provide a reliable estimate of drift velocity and correlation scales over a range of wavelengths from about one third to three times the antenna spacing, with realistic error estimates on each parameter. “Dispersive motions” similar to those reported by other workers are observed even when the model contains no features which can be sensibly described by dispersion; it must therefore be presumed that the dispersion analysis of fading records is not necessarily a physically meaningful procedure.

On the analysis and interpretation of spaced‐receiver measurements of transionospheric radio waves

“…Indeed, the original methods of Briggs et al [1950] gives a measure of the random drift component as well as the mean drift. However, because the random component does not admit a concise physical interpretation, it is not used much now [Wright and Pitteway, 1978].…”

On the accuracy and interpretation of Dynasonde virtual height measurements

“…The variability is accompanied by changes of the maximum amplitude itself; both properties are aspects of the familiar 'fading,' or scintillation, of ionospheric echoes. Now it can be demonstrated by high-resolution 'angle-of-arrival' calculations from actual measurements [e.g., Wright et al, 1976a, b; Wright and Pitteway, 1979b)], and as well by computer simulation [ Wright and Pitteway, 1978], that fading echoes return from a region considerably wider than the first Fresnel zone. Space-average methods [e.g., Golley and Rossiter, 1970, Section 5] give approximately the same result as the time-average correlation methods quoted above.…”

“…More precise work demands some statistical treatment to smooth the 'geophysical noise' and to correct for dispersion which is, after all, measurable in multifrequency soundings. On the other hand, the noise itself contains important information on ionospheric small-scale structure and provides a tracer for ionospheric motions [Wright and Pitteway, 1978]. It should also be noted that echo amplitude comparisons, over the same Af as employed here for stationary-phase group path estimations, are valuable for estimating the vertical component of ionospheric motions [Wright and Fedor, 1969;Wright et al, 1976b].…”

Real‐time data acquisition and interpretation capabilities of the Dynasonde: 1. Data acquisition and real‐time display

“…The radio frequency, receiving antenna location and orientation, and the clock time of each echo, of course, are independent variables already known precisely by the Dynasonde. In addition, we wish also to obtain the spatial variation of echo amplitude and phase over a base line comparable with the radio wavelength [Wright and Pitteway, 1978]. With only one receiver, multiple antenna sampling requires multiple pulses per frequency.…”