Study of the lower ionosphere using partial reflection: 1. Experimental technique and method of analysis

Abstract

The amplitude of weak echoes partially reflected from ionization irregularities in the height range 50-100 km are recorded. By utilizing two frequencies, 2.66 and 627 Mc/s, and recording the amplitudes of both the ordinary and extraordinary component waves, information is obtained about electron density and electron collision frequency in this height range under both normal and abnormal conditions. The method of analysis (discussed in detail in this paper) is essentially similar to that developed by Gardner and Pawsey, except that the generalized magnetoionic formulas, which take into account the energy dependence of the collision cross section, are employed. The results being obtained are believed to be more accurate in detail than those obtained by other ground-based techniques. Introduction. Our knowledge of electron densities and electron collision frequencies in the lower ionosphere (50-100 km) is relatively meager, partly because of observational limitations and partly because of difficulties in inter-preting the observational data that have been obtained. Under normal conditions the electron number densities are so low that low frequencies are needed for reflection in this height range. Despite an abundance of experimental data, few results have emerged from these studies. Under abnormal conditions the attenuation of radio waves propagating within the region can become so great that radio reflections, other than from the base of the ionosphere, are not obtained. The dynamic range of changes, even under normal conditions, is large, since the electron density and collision frequency change by about four orders of magnitude in the height range 50-100 km.The relatively high gas densities make environmental measurements with sounding rockets difficult, and most experiments have therefore been designed to provide information about the ionosphere at heights above 100 km. A few results have been obtained for the normal D region [Aikin et al., 1963; Kransnuskin and Kox With the University of Brisbane, Queensland, Australia (work performed while on sabbatical leave to DRTE during 1961). lesnikov, 1962], but these are less reliable than those obtained at times when radio-wave absorption was great [Kane, 1961; Jespersen et al., 1963].The magnitude of the electron density and its variation with height is roughly known, but superimposed on a general increase with height are important structural features, the dynamic changes of which cannot be studied by means of rockets. There is thus a need for a reliable means of studying the lower ionosphere by ground-based experiments. In recent years two new techniques have been developed for studying the D region. One of these, the ionospheric wave interaction experiment [Fejer, 1955; Barrington and Thrane, 1962] has given useful results, but there are major difficulties, both in the experimental technique and in the interpretation of the data. Another method utilizes the partial reflection of ordinary and extraordinary component waves from scatterers within the D region [Gardner ...

Relation between lower ionospheric electron density profiles and cosmic noise absorption during auroral zone disturbances.

“…The electron density profiles in the D and E region can be measured by various techniques such as a low frequency sounder (WATTS, 1958;SHELLMAN, 1970;WAKAI, 1971), the cross-modulation method (HOLT et al, 1962), partial reflection method (BELROSE and BURKE, 1964;HAUG, 1966;BELROSE et al, 1972), riometer observation (PARTHASARATHY et al, 1963;LERFALD et al, 1964), radio wave absorption measurements (ELLING, 1974), incoherent scatter radar (BANKS et al, 1974), phase measurement of VLF propagation (RINNERT, 1973), and VHF propagation (WATKINS and ESSEX, 1973). Also, the direct measurement of the ionosphere by using sounding rocket is a powerful method (JESPERSEN et al, 1964(JESPERSEN et al, , 1966MECHTLY and SMITH, 1970;SECHRIST, 1970;DERBLOM and LADELL, 1973).…”

Retrieval of mesospheric electron densities using an optimal estimation inverse method

“…(1) (Belrose and Burke, 1964;Gregory and Manson, 1969;Flood, 1968;von Biel, 1995von Biel, , 1999. The numerator of Eq.…”

“…Electron density (Ne(z)) proÿles have been retrieved using either the di erential absorption (DA) method (e.g. Gardner and Pawsey, 1953;Belrose and Burke, 1964;Gregory and Manson, 1969;von Biel, 1995von Biel, , 1999 or the di erential phase (DP) method (von Biel et al, 1970;Austin, 1971).…”

Partial Reflection Experiment: Operational and Data Reduction Techniques.

“…The first, used by Gardner and Pawsey (1953) and Belrose and Burke (1964), is to take the logarithm of equation (7) and then obtain a series of coupled difference equations which can be solved for a slab-wise approximation to the electron density at each height h. Flood, in 1968, suggested use of a polynomial solution for electron density to provide a least squared fit to the logarithm of (-)…”

“…Although the Belrose and Burke (1964) formula was used, the collisional frequency profile was incorrect, the refractive index formula was not the best available and th6 data were ieduced by logarithmically differencing measured values of Ax/A 0 at 2-kilometer altitude intervals. The Physical Science Laboratory (NMSU) were aware of the errors associated with the differencing procedure and had suggested alternate methods of data reduction.…”