We present a technique for determination of ionospheric parameters based on automatic interpretation of ionograms of ionosphere vertical sounding (VS). Ionograms are interpreted using the points with significant amplitudes that were detected after the secondary data processing, results of modelling the VS signal height-frequency characteristic (HFC) being used. We developed algorithms to extract HFC tracks of signals reflected from E, F1 and F2-layers. These algorithms are based on the analysis of signal amplitude characteristics and plotting distribution histograms of points falling into the HFC model mask when the latter is moved over the ionogram. The algorithm to detect tracks of signals reflected from sporadic layers is implemented separately. From the resultant VS HFC, one can estimate ionospheric parameters and calculate electron density profile.
KEYWORDS: Reflection, Einsteinium, Algorithm development, Beam path, Signal processing, Signal detection, Wave propagation, Signal to noise ratio, Radio propagation, Modeling
We consider the algorithms for interpreting data of ionosphere oblique sounding (OS) by using continuous chirp signal. Ionograms are interpreted using the points with significant amplitudes that were detected after the secondary data processing, results of modelling the OS signal distance-frequency characteristic (DFC) being used. We developed hybrid algorithms to extract DFC tracks of signals reflected from F1 and F2-layers. These algorithms are based on the analysis of signal amplitude characteristics and plotting distribution histograms of points falling into the DFC model mask when the latter is moved over the ionogram. Algorithms to extract tracks of signals reflected from sporadic layers are given a separate consideration. Using the results of ionogram interpretation, one can detect the maximum observed frequencies of signal propagation modes on radio path.
We present a method to determine spatial distribution of the ionospheric electron density based on data of vertical (VS), oblique (OS), and backscatter (BS) sounding with a continuous chirp signal. Initial data represent the results of automatic processing and interpretation of ionograms, from which we calculate the height-frequency characteristics (HFC) of vertical sounding in the points selected on the sphere. From HFC tracks, we determine the ionospheric parameters and calculate the electron density profiles. This allows reconstruction of electron density spatial distribution within the sector of backscatter sounding and the region of HF radio paths. The resultant ionospheric parameters are used to correct ionospheric model IRI.
In this work, we evaluate the accuracy characteristics of the automatic interpretation program complex of vertical sounding (VS) data for June 2014. We calculate relative errors of the automatic interpretation complex and diurnal variations of manual and automatic interpretations by the foF2, foF1, and foEs parameters. The mean relative errors of the automatic interpretation complex for June 2014 do not exceed 1.5%, and the standard deviation is 5-6%.
The methods for determining and correction of ionosphere parameters by real-time data of vertical and backscatter data sounding (VS and BS) by continuous chirp signal are presented. The input data are forecast ionosphere parameters and processing and interpretation results for VS and BS ionograms: VS height-frequency characteristic (HFC) and the leading edge of backscatter signal. On the base of the leading edge of BS signal one can calculate VS HFC for given points on the sphere in the sounding sector. On the base of HFC tracks the counting of ionosphere parameters is carried out. On the base extrapolation of the ratio of real to forecast values of ionosphere layer critical frequencies with account of layer geometrical parameters the correction of ionosphere parameters in given sphere points is carried out.
The study is focused on numerical modeling of vertical ionograms in horizontally non-stratified ionosphere. We have considered the F2-layer ionospheric disturbance shifted horizontally from the sounding point. The presence of this kind of disturbance is related to off-vertical reflections and, hence, multipath propagation. We have investigated the ionogram additional trace that is formed due to off-vertical ray paths. Variations in the disturbance amplitude and related changes in the shape of additional trace have been considered. Typical ray paths are presented that form additional traces in the ionogram.
The results of signal shape study for backscatter ionosphere sounding (BS) depending on conditions of radio waves propagation and electric properties of earth surface are given. The experimental BS data obtained in different seasons of the year on the basis of multifunctional chirp ionosonde developed in ISTP SB RAS were analyzed. For analysis and interpretation of BS signals on ionograms the modeling results of chirp signal characteristics under backscatter ionosphere sounding in the framework of waveguide approach were used. The most characteristic types of ionograms were identified and conditions for the appearance of one or another type were established depending on the time of day, the season, the direction of sounding and the medium state.
The paper presents a comprehensive algorithm to calculate characteristics of backscatter signals (BS) within the waveguide approach. The algorithm input parameters are profiles of electron density and effective frequency of collisions that are calculated from IRI model, electric parameters and the earth surface scattering coefficient. Based on the comprehensive algorithm, one can calculate amplitude characteristics of BS signals, including the signal time base using angular coefficients of radio wave scattering from rough surface. Simulation is performed for given two-way antenna-feeders. We implemented real-time algorithms to determine the BS signal leading edge and the skip zone border. Results of simulating signal characteristics are used to analyze and interpret BS ionograms obtained from the chirp ionosonde of the Institute of Solar-Terrestrial Physics SB RAS.
Algorithm of determining ionospheric parameters from current data of backscatter sounding (BS) with continuous chirp signal is presented. Input parameters are frequency dependences of the signal propagation group path that were obtained after processing and interpretation of BS ionograms. Algorithm of BS signal leading edge inversion to parameters of electron density quasi-parabolic profile is implemented on the basis of comparing experimental and calculated minimum delays of scattered signals, bound to distance to the skip zone border.
The results of operative diagnostics for ionosphere on the base of backscatter sounding received via chirp ionosonde are presented. The results of identification for registered signals and creation of tracks are basic data for determination of maximum usable frequencies and distant-frequency characteristics of one-hop mode 1F2 for oblique propagation on the given grid of ranges, restoration of ionosphere parameters in the direction of sounding. The algorithm for transformation of the received characteristics for oblique sounding to the height-frequency characteristic of vertical sounding with the subsequent restoration of electronic concentration profile is realized.
KEYWORDS: Backscatter, Wave propagation, Diagnostics, Data modeling, Data processing, Signal processing, Image processing, Image compression, Data compression, Interference (communication)
We present techniques and algorithms for processing and interpretation of backscatter ionosphere sounding ionograms received on chirp ionosonde. The processing of experimental ionograms is carried out on the basis of basic data filtration with the subsequent compression by method of the cellular automaton. The interpretation technique for ionograms is based on use of modeling results for frequency dependences on the minimum group way in the mode of the long-term forecast and results of experimental data processing. We also present the results of operative diagnostics of HF radio channel on the base of current backscatter sounding data.
On the base of the space-distributed multipurpose chirp ionosonde effects of solar flare influence on conditions of HF signals distribution in the northeast region of Russia were registered on February 25, 2014. The absorption increase in D – ionosphere areas during flare due to splash in x-ray radiation was shown in disappearance of the signals corresponding to modes with multiple reflections from ionospheric layer both for the ionograms of oblique and vertical sounding. In the period of a magnetic storm on February 27, 2014 on the oblique sounding ionograms on paths Magadan – Irkutsk and Khabarovsk – Irkutsk in evening and night hours of local time, were observed additional signals with abnormally big delay. The amplitude relief of abnormal signals was characterized by strong diffusion, and frequencies exceeded the maximal observed frequencies of standard propagation modes.
KEYWORDS: Solar radiation models, Solar processes, Wave propagation, X-rays, Ionization, Radio propagation, Absorption, Data modeling, Atmospheric physics, RF communications
The results for modeling of HF radio waves propagation characteristics are given for the periods of solar flares 25.02.2014, 25.10.2013, 13-14.05.2013. The distance–frequency and amplitude-frequency propagation characteristics are calculated on the base of the complex algorithm which includes modules of ionosphere and plasmasphere global models and radio waves propagation model. The results of calculations were compared with experimental data of oblique ionosphere sounding obtained by chirp ionosonde on paths Magadan – Irkutsk, Khabarovsk – Irkutsk and Norilsk – Irkutsk.
KEYWORDS: Magnetism, Micro optical fluidics, Wave propagation, Radio propagation, Magnetosphere, Solar processes, Plasma, Atmospheric physics, Solar radiation models, Data modeling
The disturbances of ionospheric radio channel during 17–24 March 2015 magnetic storm are investigated. The heliospheric sources which caused the storm are considered. Based on space-distributed multipurpose chirp ionosonde data effects of geomagnetic disturbances influence on conditions of HF signal propagation are studied.
The paper deals with techniques and algorithms of near real-time diagnostic software for estimating ionospheric parameters at a radio path midpoint based on data obtained from oblique sounding by a continuous chirp signal. We conducted a statistical analysis of precision characteristics of automatic determination of the critical frequency f0F2 at the path midpoint, using chirp ionosonde data.
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