Radio Wave Propagation Conditions Research Articles

Estimation of Radio Wave Propagation Conditions above the Sea Surface by Radiometric Measurements at Grazing Angles

Estimation of Radio Wave Propagation Conditions above the Sea Surface by Radiometric Measurements at Grazing Angles

On the Use of Acoustic and Radioacoustic Methods of PBL Remote Sensing for Assessment of Radiowave Propagation Conditions

On the Use of Acoustic and Radioacoustic Methods of PBL Remote Sensing for Assessment of Radiowave Propagation Conditions

Influence of the lower region of the enhanced ionization produced by a space nuclear explosion on radio wave propagation

[1] Propagation of radio waves through the region of enhanced (cold) ionization of the ionosphere formed below the ionospheric E layer by the X ray and penetrating radiation of a space nuclear explosion is considered. A method to calculate the field and the main radiophysical effects caused by this region is developed. The method makes it possible to calculate the above indicated effects for a wide range of the equivalents and altitudes of the nuclear charge explosions. Asymptotic formulae are obtained for the attenuation determining the conditions of radio wave propagation through the lower region of the enhanced ionization. The formulae make it possible to estimate the effects with the error not exceeding the error in the initial data on spatial-time distributions of the electron concentration.

Analysis of Propagation Conditions of ELF Radio Waves on the “Zeus”–Transbaikalia Path

We consider the results of measurements of the absolute values of horizontal electric and magnetic components of the electromagnetic field of the “Zeus” ELF radio facility at frequencies 33, 44, 82, and 188 Hz, carried out in Transbaikalia. Electromagnetic-field variations during 17 semidiurnal sessions (about 204 hours of synchronous records) are analyzed. The length of the “Zeus”–Transbaikalia path is approximately 4000 km.

A comparison of results derived from scaling VS chirp-ionosonde ionograms with the international reference ionosphere (IRI)

The results derived from processing vertical-incidence ionograms obtained with the chirp-ionosonde at Irkutsk for different winter time intervals (February) and at equinox are presented. The peak height hmF2 was determined by Dudeney's formula based on ionogram parameters, including the coefficient M(3000). The algorithm is suggested for determining the coefficient M(3000) in the automatic mode using the conventional form of the transfer curve method without invoking a standard transparency called the “transfer curve”. The parameters foF2 and hmF2 are compared with the international reference ionosphere (IRI-95) model. It is found that in most cases the values of the foF2 and hmF2 parameters, calculated in the IRI-95 model, are similar to the median ones. It is confirmed that for practical purposes where it is necessary to know the radio wave propagation conditions along the propagation path, the IRI model is convenient and attractive.

On the collocation between dayside auroral activity and coherent HF radar backscatter

<strong class="journal-contentHeaderColor">Abstract.</strong> The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of <u>&gt;</u> 220 m s^–1 proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the <u>&gt;</u> 220 m s^–1 spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1) improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2) a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3) a firmer physical rationale as to why the good correlation observed should theoretically be expected.<br><br><b>Key words:</b> Ionosphere (ionospheric irregularities; polar ionosphere)

On the collocation between dayside auroral activity and coherent HF radar backscatter

Abstract. The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of &gt; 220 m s–1 proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the &gt; 220 m s–1 spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1) improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2) a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3) a firmer physical rationale as to why the good correlation observed should theoretically be expected.Key words: Ionosphere (ionospheric irregularities; polar ionosphere)

Mechanisms of tropospheric microwave propagation for a linear segmented profile of the refractive index

The mechanisms of tropospheric microwave propagation for a linear segmented profile of the refractive index are summarized. There is an attempt to generalize the profile of this type and investigate different radio wave propagation conditions from the standpoint of the coherence theory of microwave tropospheric diffraction. In particular, there is discussion concerned with the whispering gallery modes in the troposphere. It seems unlikely these will be excited. Thus, the reflections from the atmospheric layers and the trapped modes under superrefraction conditions account mainly for the long distance tropospheric propagation from this standpoint.

A radiometeorological study of the Chios-Lemnos line of sight radio link

This study deals with the conditions of radio wave propagation in the link between the islands Chios and Lemnos and especially with the influence of weather situations upon this propagation. The field fading forms have been classified into three typesA, B andC which have an annual course of large amplitude. TypesA andB show their maximum frequency during the cold months of the year and their minimum during the warm months, while the typeC shows an annual course inverse to the courses of the typesA andB. This can be explained if it is taken into consideration that in the eastern Mediterranean the weather situations during the warm season are absolutely different from those of the cold season. Finally for the months January, April, July and October a correlation between the prevailing weather situations and the occurence of theA, B, C fading forms has been attempted, the main results of which were that the typeC occurs with weak winds, or with clear and calm weather as well as under the blowing of the Etesian winds, while the typeA is almost certainly due to the anticyclonic extensions during the cold season of the year and generally to the strong winds of the north sector.

A Method of Representing Radio Wave Propagation Conditions

The daylight radio transmission conditions across the North Atlantic Ocean in 1930 for wavelengths of 10,000 to 20,000 m (15-30 kc) are shown in a table based on the daily observations of the signal strength of seven European high power stations taken in Washington. It is expected that similar tables of daily transmission conditions for the years beginning with 1924 will soon be ready for publication. The object of this form of tabulation is to furnish a ready means of comparison of radio conditions with other natural phenomena-sun spots, magnetic storms, weather, etc.