Modelling of HF wave propagation in the vicinity of quasicritical rays in the disturbed ionosphere

Ерухимов, Л. М.; Ponyatov, A. A.; Uryadov, V. P.; Ivanov, V. A.; Shumaev, V. V.; Egorov, I. B.; Cherkashin, Yu. N.

doi:10.1007/bf02676706

Cited by 2 publications

(3 citation statements)

References 5 publications

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“…At the same time, the modeling shows that the conditions of the formation of "cusps" in the distance-frequency characteristics are rather stringent and depend on the TID relative amplitude, the wavelength of the disturbance, and the direction of its propagation with respect to the radio-path orientation. This agrees with the data in [3] in which the significant influence of the inclination of the TID phase front on the conditions of the formation of the distance-frequency characteristics in the vicinity of the MOF is also noted. For example, the TID parameters in Eq.…”

Section: Modelingsupporting

confidence: 90%

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Oblique Sounding and Modeling of the Ionospheric HF Channel

Vertogradov

Uryadov

Vertogradov

2005

Radiophys Quantum Electron

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We present the results of experimental studies of the distance-frequency and amplitude-frequency characteristics of the ionospheric HF channel on mid-latitude paths of oblique chirp sounding. It is shown that the maximum observed frequencies (MOFs) are subject to short-period variations with the quasi-periods from 30 min to 2 h. The amplitude of the MOF variations reaches 2 MHz and can increase up to 5-8 MHz on the Cyprus-Rostov-on-Don one-hop path in the sunrisesunset time. It is established that the MOF fluctuations are accompanied by pronounced "cusp" features occurring in the upper rays and moving with time to the region of shorter delays, i.e., from lower to higher frequencies. The amplitude-frequency characteristics of individual propagation modes undergo deep fluctuations (up to 20-30 dB) whose quasi-period and depth depend on the frequency. It is shown that the appearance of fluctuations is caused by interference of the unresolved rays within the limits of one propagation mode. Based on the modeling, it is shown that "cusps" in oblique-sounding ionograms are due to the influence of traveling ionospheric disturbances (TIDs). The TID parameters are estimated. It is shown that conditions of the formation of "cusps" in the distance-frequency characteristics depend on the TID amplitude, the wavelength of the disturbance wave, and the direction of its phase front with respect to the propagation path. The effect of quasi-regular frequency modulation of the Pedersen mode with a period of 250-300 kHz on the Cyprus-Rostov-on-Don chirp-sounding path is found. Altitude stratification of the ionosphere near the F-layer maximum, which is responsible for the focusing and defocusing of the Pedersen mode, is estimated. It is established that the stratification scale amounts to approximately 200-250 m.

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Section: Modelingsupporting

confidence: 90%

“…(see [2] and references therein). In recent years, the method of oblique sounding by a chirp signal (chirp sounding) has been used [3]. To estimate the TID parameters and forecast their influence on the characteristics of HF signals, the modeling of the ionospheric channel in the quiet and disturbed ionosphere plays the key role [4].…”

Section: Introductionmentioning

confidence: 99%

Oblique Sounding and Modeling of the Ionospheric HF Channel

Vertogradov

Uryadov

Vertogradov

2005

Radiophys Quantum Electron

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“…Comparison of the measurement results of the MOF variations during a magnetic storm and under quiet conditions shows that in the former case, the amplitude of the MOF variations significantly increases, the amplitude of rapid variations with period shorter than 15 min also increases, and the pulsed temporal behavior of the MOF is observed, which is indicative of wave processes occurring in the ionosphere under geomagnetic disturbances. The estimates based on simulations of the ionospheric propagation of HF waves with allowance for the traveling ionospheric disturbances and obtained using the method described in [33] show that the observed modulation of the distance-frequency characteristic near the MOF can result from wave-like disturbances of the electron number density with an amplitude of 20-30% of the background level. The large-scale MOF variations observed at approximately 11:00 to 14:00 UT can be related to passage of the terminator along the propagation path.…”

Section: Simulationmentioning

confidence: 99%

Features of propagation of HF signals on mid-latitude paths under conditions of geomagnetic disturbances

Uryadov

Kurkin

Vertogradov

et al. 2004

Radiophys Quantum Electron

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We present the results of experimental studies of the features of HF-signal propagation on obliquesounding paths in the Eurasian longitude sector between England and Magadan during geomagnetic disturbances. The joint analysis of the satellite data and the data of vertical and oblique sounding of the ionosphere shows that the appearance of additional signals during magnetic disturbances can be stipulated by refraction of radio waves in the region of the auroral oval and the main ionospheric trough as well as by scattering from small-scale magnetic-field-aligned irregularities near the equatorial boundary of the auroral oval. Based on calculations and comparison with experimental data of oblique sounding of the mid-latitude ionosphere, we identify the "lateral" spreading signals registered on the Magadan -Irkutsk and Inskip (England) -Rostov-on-Don paths as signals scattered by small-scale field-aligned irregularities whose location coincides with the southern boundary of the auroral oval. We show that the Russian and global chirp-ionosonde networks are promising for studying the dynamics of the main ionospheric trough and the auroral oval during geomagnetic disturbances as a manifestation of space weather in the near-Earth environment.

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Modelling of HF wave propagation in the vicinity of quasicritical rays in the disturbed ionosphere

Cited by 2 publications

References 5 publications

Oblique Sounding and Modeling of the Ionospheric HF Channel

Oblique Sounding and Modeling of the Ionospheric HF Channel

Features of propagation of HF signals on mid-latitude paths under conditions of geomagnetic disturbances

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