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1
Li, Qingfeng, Zeyun Li e Hanxian Fang. "Using 3D Ray Tracing Technology to Study the Disturbance Effect of Rocket Plume on Ionosphere". Atmosphere 13, n. 7 (20 luglio 2022): 1150. http://dx.doi.org/10.3390/atmos13071150.
Testo completoAbstract (sommario):
In this paper, the initial neutral atmospheric parameters, background ionospheric parameters and geomagnetic field parameters of the ionosphere are obtained by NRLMSISE-00 model, IRI-2016 model and IGRF-13 model, respectively. Considering the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, a three-dimensional dynamic model of chemical substances released by rocket plume disturbing the ionosphere is constructed. The influence of the disturbance on the echo path of high frequency radio waves with different incident frequencies is simulated by using three-dimensional digital ray-tracing technology. Using this model, the process of ionospheric disturbance caused by the main chemical substances H2 and H2O in the rocket plume under three different release conditions: fixed-point release at 300 km, vertical path at 250–350 km and parabolic path at 250–350 km, and the influence of the ionospheric cavity on the radio wave propagation of high frequency radio waves at different frequencies are simulated. The main purpose of the article is to focus on the effect of the cavity generated by the rocket exhaust on the propagation of radio waves. It mainly studies the perturbation effect on the ionosphere under different release conditions, considers the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, and establishes the three-dimensional dynamics of the ionospheric electron density and the spatiotemporal distribution of the plume plasma learning model. Finally, the three-dimensional ray-tracing algorithm is used to simulate the propagation path of the radio wave through the disturbance area. We considered three different release conditions, including fixed-point release, vertical path and parabolic path. The ionospheric disturbances produced by these different releases are compared and analyzed, and their effects on the propagation path of radio waves are studied.
2
Krasheninnikov, I. V., e V. N. Shubin. "Features of Forecasting the Operation of Ionospheric Radio Lines in Upper Rays Modes". Геомагнетизм и аэрономия 63, n. 4 (1 luglio 2023): 473–80. http://dx.doi.org/10.31857/s0016794023600096.
Testo completoAbstract (sommario):
The frequency dependence of transmitted information qualitative indicators is analyzed on theexample of two meridional radio links: single-hop (~2600 km) and dominant two-hop (~5100 km) for basicmodes of radio wave propagation in the ionosphere. It is shown that the presence of highly efficient receivingtransmittingantennas in a radio communication system leads to the need to take the existence of a priori energeticallyextremely weak modes into account in the problem of radio path specification statement. In thiscase, we consider those formed exclusively by the mechanism of radiation transfer along the upper-angles raytrajectories in the ionospheric propagation of radio waves. If the angles of departure and arrival for suchmodes and the directions of the main lobes of the antenna patterns at the end points of the radio path coincide,the signal-to-noise ratio for the wave field can reach the required threshold value and ensure the successfuloperation of the radio communication system. This may expand the upper frequency limit for the passageof radio waves in the transition regions of jump propagation of radio waves in the ionosphere; it shouldbe taken into account in forecasting the operation of ionospheric radio links.
3
Yang, Li-Xia, Chao Liu, Qing-Liang Li e Yu-Bo Yan. "Electromagnetic wave propagation characteristics of oblique incidence nonlinear ionospheric Langmuir disturbance". Acta Physica Sinica 71, n. 6 (2022): 064101. http://dx.doi.org/10.7498/aps.71.20211204.
Testo completoAbstract (sommario):
Based on the generalized Zakharov model, a numerical model of electromagnetic wave propagating in the ionosphere at different angles is established by combining the finite difference time domain (FDTD) method of obliquely incident plasma with the double hydrodynamics equation and through equivalently transforming the two-dimensional Maxwell equation into one-dimensional Maxwell equation and the plasma hydrodynamics equation. In this paper. the dominant equation of Z-wave in obliquely incident nonlinear ionospheric plasma having been analyzed and deduced, the FDTD algorithm suitable for calculating the propagation characteristics of ionospheric electromagnetic wave is deduced. The simulation results prove the accuracy and effectiveness of this method for the Langmuir disturbance caused by electromagnetic wave heating the ionosphere at a small inclination angle. The results show that under small angle incidence, the high-power high-frequency electromagnetic wave excites the Langmuir wave near the O-wave reflection point in the ionospheric plasma. At the same time, the wave particle interaction causes the O-wave to convert into Z-wave and propagate into the higher region of the ionosphere. In this work, the electromagnetic wave propagation characteristics are further studied based on ionospheric plasma, which is helpful in laying the foundation of numerical algorithm for comprehensively and in depth analyzing the influence of ionospheric Langmuir disturbance on ionospheric radio wave propagation characteristics.
4
LaBelle, J. "High-latitude propagation studies using a meridional chain of LF/MF/HF receivers". Annales Geophysicae 22, n. 5 (8 aprile 2004): 1705–18. http://dx.doi.org/10.5194/angeo-22-1705-2004.
Testo completoAbstract (sommario):
Abstract. For over a decade, Dartmouth College has operated programmable radio receivers at multiple high-latitude sites covering the frequency range 100-5000kHz with about a 1-s resolution. Besides detecting radio emissions of auroral origin, these receivers record characteristics of the ionospheric propagation of natural and man-made signals, documenting well-known effects, such as the diurnal variation in the propagation characteristics of short and long waves, and also revealing more subtle effects. For example, at auroral zone sites in equinoctial conditions, the amplitudes of distant transmissions on MF/HF frequencies are often enhanced by a few dB just before they fade away at dawn. The polarization and/or direction of the arrival of ionospherically propagating signals in the lower HF range (3-5MHz) show a consistent variation between pre-midnight, post-midnight, and pre-dawn conditions. As is well known, magnetic storms and substorms dramatically affect ionospheric propagation; data from multiple stations spanning the invariant latitude range 67-79° reveal spatial patterns of propagation characteristics associated with magnetic storms and substorms. For example, in the hours preceding many isolated substorms, favorable propagation conditions occur at progressively lower latitudes as a function of time preceding the substorm onset. For some of these effects, explanations follow readily from elementary ionospheric physics, but understanding others requires further investigation.Key words. Magnetospheric physics (annual phenomena) – Radio science (ionosphere propagation; radio-wave propagation)6
5
Pavelyev, A. G., Y. A. Liou, K. Zhang, C. S. Wang, J. Wickert, T. Schmidt, V. N. Gubenko, A. A. Pavelyev e Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques 5, n. 1 (4 gennaio 2012): 1–16. http://dx.doi.org/10.5194/amt-5-1-2012.
Testo completoAbstract (sommario):
Abstract. By using the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data, a description of different types of the ionospheric impacts on the RO signals at the altitudes 30–90 km of the RO ray perigee is given and compared with the results of measurements obtained earlier in the satellite-to-Earth communication link at frequency 1.5415 GHz. An analytical model is introduced for describing propagation of radio waves in a stratified medium consisting of sectors with spherically symmetric refractivity distribution. This model gives analytical expressions for the phase, bending angle, and refractive attenuation of radio waves and is applied to the analysis of radio wave propagation phenomena along an extended path including the atmosphere and two parts of the ionosphere. The model explains significant amplitude and phase variations at altitudes 30–90 km of the RO ray perigee and attributes them to inclined ionospheric layers. Based on this analytical model, an innovative technique is introduced to locate layers in the atmosphere and ionosphere. A necessary and sufficient criterion is obtained for a layer to be located at the RO ray perigee. This criterion gives both qualitative and quantitative estimation of the displacement of an ionospheric and/or atmospheric layer from the RO ray perigee. This is important, in particular, for determining the location of wind shears and directions of the internal wave propagation in the lower ionosphere, and, possibly, in the atmosphere.
6
Leyser, Thomas B., H. Gordon James, Björn Gustavsson e Michael T. Rietveld. "Evidence of <i>L</i>-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith". Annales Geophysicae 36, n. 1 (21 febbraio 2018): 243–51. http://dx.doi.org/10.5194/angeo-36-243-2018.
Testo completoAbstract (sommario):
Abstract. The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The CASSIOPE (CAScade, Smallsat and IOnospheric Polar Explorer) spacecraft in the topside ionosphere above the F-region density peak detected transionospheric pump radiation, although the pump frequency was below the maximum ionospheric plasma frequency. The pump wave is deduced to arrive at CASSIOPE through L-mode propagation and associated double (O to Z, Z to O) conversion in pump-induced radio windows. L-mode propagation allows the pump wave to reach higher plasma densities and higher ionospheric altitudes than O-mode propagation so that a pump wave in the L-mode can facilitate excitation of upper hybrid phenomena localized in density depletions in a larger altitude range. L-mode propagation is therefore suggested to be important in explaining the magnetic zenith effect. Keywords. Space plasma physics (active perturbation experiments)
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Danskin, D. W., A. V. Koustov, T. Ogawa, N. Nishitani, S. Nozawa, S. E. Milan, M. Lester e D. Andre. "On the factors controlling occurrence of F-region coherent echoes". Annales Geophysicae 20, n. 9 (30 settembre 2002): 1385–97. http://dx.doi.org/10.5194/angeo-20-1385-2002.
Testo completoAbstract (sommario):
Abstract. Several factors are known to control the HF echo occurrence rate, including electron density distribution in the ionosphere (affecting the propagation path of the radar wave), D-region radio wave absorption, and ionospheric irregularity intensity. In this study, we consider 4 days of CUTLASS Finland radar observations over an area where the EISCAT incoherent scatter radar has continuously monitored ionospheric parameters. We illustrate that for the event under consideration, the D-region absorption was not the major factor affecting the echo appearance. We show that the electron density distribution and the radar frequency selection were much more significant factors. The electron density magnitude affects the echo occurrence in two different ways. For small F-region densities, a minimum value of 1 × 1011 m-3 is required to have sufficient radio wave refraction so that the orthogonality (with the magnetic field lines) condition is met. For too large densities, radio wave strong "over-refraction" leads to the ionospheric echo disappearance. We estimate that the over-refraction is important for densities greater than 4 × 1011 m-3. We also investigated the backscatter power and the electric field magnitude relationship and found no obvious relationship contrary to the expectation that the gradient-drift plasma instability would lead to stronger irregularity intensity/echo power for larger electric fields.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere)
8
Mabie, Justin, e Terence Bullett. "Multiple Cusp Signatures in Ionograms Associated with Rocket-Induced Infrasonic Waves". Atmosphere 13, n. 6 (12 giugno 2022): 958. http://dx.doi.org/10.3390/atmos13060958.
Testo completoAbstract (sommario):
We are interested in understanding how and when infrasonic waves propagate in the thermosphere, specifying the physical properties of those waves, and understanding how they affect radio wave propagation. We use a combination of traditional ionosonde observations and fixed frequency Doppler soundings to make high quality observations of vertically propagating infrasonic waves in the lower thermosphere/bottom side ionosphere. The presented results are the first simultaneous observations of infrasonic wave-induced deformations in ionograms and high-time-resolution observations of corresponding plasma displacements. Deformations in ionospheric echoes, which manifest as additional cusps and range variations, are shown to be caused by infrasonic wave-induced plasma displacements.
9
Riabova, S. A., E. V. Olshanskaya e S. L. Shalimov. "Response of the Lower and Upper Ionosphere to Earthquakes in Turkey on February 6, 2023". Физика земли 2023, n. 6 (1 novembre 2023): 153–62. http://dx.doi.org/10.31857/s0002333723060182.
Testo completoAbstract (sommario):
Abstract—Ground-based magnetometers and ionospheric radio probing by means of GPS were used to analyze and interpret specific variations of the geomagnetic field and the total electron content of the ionosphere during strong catastrophic earthquakes in Turkey on February 6, 2023. It is shown that the ionospheric responses to these earthquakes recorded at distances of 1200–1600 km from the epicentre in the lower ionosphere and at distances of up to 500 km from the epicentre in the upper ionosphere can be interpreted in terms of the propagation of the Rayleigh seismic wave and atmospheric waves – shock, acoustic and internal, that is, those waves that are generated by the earthquake itself. The energy of seismic events was estimated from the ionospheric response.
10
Waters, C. L., T. K. Yeoman, M. D. Sciffer, P. Ponomarenko e D. M. Wright. "Modulation of radio frequency signals by ULF waves". Annales Geophysicae 25, n. 5 (4 giugno 2007): 1113–24. http://dx.doi.org/10.5194/angeo-25-1113-2007.
Testo completoAbstract (sommario):
Abstract. The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1–100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B0, giving an e×B0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF) Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.
11
Kouris, S. S., P. A. Bradley e P. Dominici. "<i>Letter to the Editor:</i> Solar-cycle variation of the daily <i>fo</i>F2 and M(3000)F2". Annales Geophysicae 16, n. 8 (31 agosto 1998): 1039–42. http://dx.doi.org/10.1007/s00585-998-1039-0.
Testo completoAbstract (sommario):
Abstract. Daily values of the ionospheric characteristics foF2 and M(3000)F2 for a given hour and month are correlated with the corresponding daily values of sunspot number using measured data collected at seven European locations. The significance of applying different-order polynomials is considered and the times are confirmed when the higher-order terms are important. Mean correlation coefficients for combined data sets over all hours, months and stations are determined, together with the standard errors of estimates. Comparisons are made with corresponding figures for monthly median values derived from the same data sets.Key words. Electromagnetics (Guided waves) · Ionosphere (Ionospheric disturbances) · Radio Science (Radio wave propagation)
12
Husin, Asnawi, e Buldan Muslim. "EFEK GELOMBANG TSUNAMI ACEH 2004 PADA GANGGUAN IONOSFER BERGERAK SKALA MENENGAH DARI PENGAMATAN JARINGAN GPS SUMATRA". Komunikasi Fisika Indonesia 16, n. 2 (31 ottobre 2019): 130. http://dx.doi.org/10.31258/jkfi.16.2.130-137.
Testo completoAbstract (sommario):
Medium Scale Travelling Ionospheric Disturbance (MSTID), thought to be manifestation of atmospheric gravity wave (AGW) in the ionospheric altitude that propagates horizontally and effects on in the electron density structure of ionosphere. These atmospheric gravity waves sourced from lower atmospheric activities such as typhoons, volcanic eruptions and tsunamis. Wave energy by its coupling induction process can travel to the ionosphere region. It has been understood that the TID's wave structure have an impact on the propagation of radio waves in the ionosphere so that it will affect the performance of navigation satellite-based positioning measurements. Based on Aceh tsunami in December 2004, this study aimed to investigation of the induction of atmospheric gravity waves in the ionosphere using total electron content (TEC) data from the Sumatra GPS network (Sumatra GPS Array, SUGAR). The detection technique of TEC changes due to AGW induction with a filter to separate medium scale disturbance at the ionospheric pierce point at an altitude of 350 km (IPP, Ionospheric Pierce Point). The results show the horizontal wavelength of a medium-scale TID around 180 ± 12 Km with a velocities of around 376 ± 9 ms-1. Based on two-dimensional map, the TID moves to the southeast.
13
Pavelyev, A. G., K. Zhang, J. Wickert, T. Schmidt, Y. A. Liou, V. N. Gubenko, A. A. Pavelyev, R. R. Salimzjanov e Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques Discussions 4, n. 2 (1 marzo 2011): 1465–92. http://dx.doi.org/10.5194/amtd-4-1465-2011.
Testo completoAbstract (sommario):
Abstract. Conditions for communication, navigation, and remote sensing in the ionosphere and atmosphere depend strongly on the ionospheric impact on the radio waves propagation. By use of the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data a description of different types of the ionospheric contributions to the RO signals at the altitudes 30–90 km of the RO ray perigee is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz. An analytical model is introduced for description of the radio waves propagation in a stratified medium consisting of sectors having the spherically symmetric distributions of refractivity. Model presents analytical expressions for the phase path and refractive attenuation of radio waves. Model is applied for analysis of the radio waves propagation effects along a prolonged path including the atmosphere and two parts of the ionosphere. Model explains significant amplitude and phase variations at the altitudes 30–90 km of the RO ray perigee as connected with influence of the inclined ionospheric layers. An innovative eikonal acceleration technique is described and applied for the identification of the inclined ionospheric layers contributions and their location. Possibility to separate the influence of layered structures from contributions of irregularities and turbulence is analyzed.
14
Keuer, Dieter. "Estimation of ionospheric reflection height using long wave propagation". Advances in Radio Science 17 (19 settembre 2019): 205–12. http://dx.doi.org/10.5194/ars-17-205-2019.
Testo completoAbstract (sommario):
Abstract. Phase height measurements of low frequency radio waves are used to study the long-term variability of the mesosphere over Europe. Phase height measurements use a characteristic pattern in field strength registration of radio waves interpreted as phase relations between sky wave and surface wave to obtain the apparent height of the reflection point, the Standard Phase Height (SPH). Based on this SPH-method a homogenized daily series was generated since 1959 at Kühlungsborn. Improvements of the measuring method show that the signal is significantly influenced by lower atmospheric layers. Mesospheric reflection is not the exclusive source of the measured behavior. Tropospheric influence can not be neglected. Taking this into account one has to conclude that the strong coherency of the SPH data to mesospheric heights is not as significant as previously assumed.
15
Altadill, David, Antoni Segarra, Estefania Blanch, José Miguel Juan, Vadym V. Paznukhov, Dalia Buresova, Ivan Galkin, Bodo W. Reinisch e Anna Belehaki. "A method for real-time identification and tracking of traveling ionospheric disturbances using ionosonde data: first results". Journal of Space Weather and Space Climate 10 (2020): 2. http://dx.doi.org/10.1051/swsc/2019042.
Testo completoAbstract (sommario):
Traveling Ionospheric Disturbances (TIDs) are wave-like propagating irregularities that alter the electron density environment and play an important role spreading radio signals propagating through the ionosphere. A method combining spectral analysis and cross-correlation is applied to time series of ionospheric characteristics (i.e., MUF(3000)F2 or foF2) using data of the networks of ionosondes in Europe and South Africa to estimate the period, amplitude, velocity and direction of propagation of TIDs. The method is verified using synthetic data and is validated through comparison of TID detection results made with independent observational techniques. The method provides near real time capability of detection and tracking of Large-Scale TIDs (LSTIDs), usually associated with auroral activity.
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Bajcetic, Jovan, Aleksandra Nina, Vladimir Cadez e Branislav Todorovic. "Ionospheric D-region temperature relaxation and its influences on radio signal propagation after solar X-flares occurrence". Thermal Science 19, suppl. 2 (2015): 299–303. http://dx.doi.org/10.2298/tsci141223084b.
Testo completoAbstract (sommario):
In this paper our attention is focused on relations between radio signal propagation characteristics and temperature changes in D-region after solar X-flare occurrence. We present temperature dependencies of electron plasma frequency, the parameter that describes medium conditions for propagation of an electromagnetic wave, and the refractive index which describes how this wave propagates. As an example for quantitative calculations based on obtained theoretical equations we choose the reaction of the D-region to the solar X-flare occurred on May 5th, 2010. The ionospheric modelling is based on the experimental data obtained by low ionosphere observations using very low frequency radio signal.
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Salikhov, Nazyf, Alexander Shepetov, Galina Pak, Serik Nurakynov, Azamat Kaldybayev, Vladimir Ryabov e Valery Zhukov. "Investigation of the Pre- and Co-Seismic Ionospheric Effects from the 6 February 2023 M7.8 Turkey Earthquake by a Doppler Ionosonde". Atmosphere 14, n. 10 (25 settembre 2023): 1483. http://dx.doi.org/10.3390/atmos14101483.
Testo completoAbstract (sommario):
During the catastrophic M7.8 earthquake in Turkey on 6 February 2023, anomalous effects were revealed in the ionosphere associated with various propagation mechanisms of seismogenic disturbance from the lithosphere up to the height of the ionosphere. Seventeen minutes after the main shock, a co-seismic disturbance was detected by a Doppler ionosonde on an inclined, 3010 km long, two-hop radio path “Kuwait—Institute of Ionosphere (Almaty)”. An appearance of acoustic waves at the height of 232 km in the ionosphere was fixed 568 s after arrival of the surface Rayleigh wave to the sub-ionospheric point, and such a delay agrees with the calculated propagation time of a vertically moving acoustic wave. The disturbance lasted 160 s, and its double amplitude was above 2 Hz, which noticeably exceeds the background fluctuation of Doppler frequency. The best coincidence between the waveforms of the Doppler signal and of the surface seismic wave was observed over the duration of the two leading periods, with correlation coefficients of 0.86 and 0.79, correspondingly. Pre-seismic effects in the ionosphere were revealed 8 days before the main shock both in the variations of the Doppler frequency and of the critical frequency f0F2. The probable origination mechanism of the pre-seismic ionospheric disturbances above the region of the earthquake preparation determined by the Dobrovolsky radius may be considered in accordance with the concept of lithospheric–atmospheric–ionospheric coupling.
18
Borisova, T. D., N. F. Blagoveshchenskaya e A. S. Kalishin. "Forecasting the conditions of the decameter radio wave propagation in the Аrctic region". Arctic and Antarctic Research, n. 3 (30 settembre 2017): 78–86. http://dx.doi.org/10.30758/0555-2648-2017-0-3-78-86.
Testo completoAbstract (sommario):
In this paper we present the results of studies the distinctive features of the decameter radio wave propagation based on the results of experimental measurements of radio wave propagation characteristics by the ionospheric oblique sounding (IOS) method and numerical simulation. An algorithm for numerical modeling the trajectory and energetic characteristics of the decameter radio wave propagation in the framework of geometric optics is described. The agreement between the simulated and experimental radio propagation parameters (for example, the values of the maximum observed frequencies) is demonstrated. It is proposed to use the developed diagnostic model of the HF radio channel for the purposes of forecasting in areas not provided with IOS stations.
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Jandieri, George, e Nika Tugushi. "Statistical Characteristics of the Temporal Spectrum of Scattered Radiation in the Equatorial Ionosphere". Journal of Environmental & Earth Sciences 5, n. 1 (13 aprile 2023): 85–94. http://dx.doi.org/10.30564/jees.v5i1.5442.
Testo completoAbstract (sommario):
On the basis of the solution of the space-time characteristic system by the method of geometric optics using symbolic calculations, analytical and numerical simulation of the propagation of the ordinary and extraordinary radio waves in the conducting equatorial ionospheric plasma was made considering the anisotropy of plasma irregularities and non-stationary nature of propagation medium. Broadening of the spectrum and the displacement of its maximum contain velocity of a turbulent plasma flow and parameters characterizing anisotropic plasmonic structures. Statistical moments of both radio waves do not depend on the absorption sign and are valid for both active and absorptive random media. Temporal pulsations and conductivity of a turbulent ionospheric plasma have an influence on the evaluation of the spectrum-varying propagation distances travelling by these waves. The new double-humped effect in the temporal spectrum has been revealed for the ordinary wave varying anisotropy coefficient and dip angle of stretched plasmonic structures. From a theoretical point of view, the algorithms developed in this work allow effective modelling of the propagation of both radio signals in the equatorial conductive ionospheric plasma, considering the external magnetic field, inhomogeneities of electron density in-homogeneities, as well as non-stationary.
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Robinson, T. R. "Effects of multiple scatter on the propagation and absorption of electromagnetic waves in a field-aligned-striated cold magneto-plasma: implications for ionospheric modification experiments". Annales Geophysicae 20, n. 1 (31 gennaio 2002): 41–55. http://dx.doi.org/10.5194/angeo-20-41-2002.
Testo completoAbstract (sommario):
Abstract. A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.Key words. Ionosphere (active experiments; ionospheric irregularities) Radio science (ionospheric propagation)
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Blagoveshchensky, D. V., e O. A. Maltseva. "Simulation of Medium Wave Propagation in the Magnetosphere". Geomagnetism and Aeronomy 62, n. 1-2 (febbraio 2022): 58–65. http://dx.doi.org/10.1134/s0016793222020049.
Testo completoAbstract (sommario):
Abstract A model of the medium of the ionosphere and magnetosphere, including the distributions of the concentrations and temperatures, collision frequencies, and magnetic field parameters, is described. The ray-tracing method was used to simulate the parameters of medium radio waves in this environment. The wave trajectories were calculated in the approximation of geometric optics. When the level of solar and geomagnetic activity and the location of the transmitter and the frequency are set, the parameters of the wave paths can be calculated. Numerical modeling of the characteristics of experimental echo signals has shown that the mechanism of magnetospheric propagation is of paramount importance. In this case, the main ionospheric trough turned out to be an unusual channel. Medium waves propagate inside the trough along the plasmapause. This is possible with sufficiently clear relationships between the positions of the trough, plasmapause, and transmitter. The considered effect of medium wave channeling can be used to diagnose the position of the trough and plasmapause.
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Isaakidis, S. A., T. D. Xenos e J. A. Koukos. "Ionospheric radio wave propagation finite element method modeling". Electrical Engineering (Archiv fur Elektrotechnik) 85, n. 5 (1 novembre 2003): 235–39. http://dx.doi.org/10.1007/s00202-003-0176-4.
Testo completo
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Blagoveshchensky, D. V., T. D. Borisova e J. W. MacDougall. "Irregular HF radio propagation on a subauroral path during magnetospheric substorms". Annales Geophysicae 24, n. 7 (9 agosto 2006): 1839–49. http://dx.doi.org/10.5194/angeo-24-1839-2006.
Testo completoAbstract (sommario):
Abstract. The impact of the main ionospheric trough, sporadic structures, gradients and inhomogeneities of the subpolar ionosphere during substorms on the signal amplitude, azimuthal angles of arrival, and propagation modes for the radio path Ottawa (Canada)-St. Petersburg (Russia) was considered. This subauroral path with the length of about 6600 km has approximately an east-west orientation. The main goals are to carry out numerical modeling of radio propagation for the path and to compare the model calculations with experimental results. Wave absorption and effects of focusing and divergence of rays were taken into consideration in the radio wave modeling process. The following basic results were obtained: The signal amplitude increases by 20–30 dB 1–1.5 h before the substorm expansion phase onset. At the same time the signal azimuth deviates towards north of the great circle arc for the propagation path. Compared with quiet periods there are effects due to irregularities and gradients in the area of the polar edge of the main ionospheric trough on the passing signals. Propagation mechanisms also change during substorms. The growth of signal amplitude before the substorm can be physically explained by both a decrease of the F2-layer ionization and a growth of the F2-layer height that leads to a decrease of the signal field divergence and to a drop of the collision frequency. Ionospheric gradients are also important. This increase of signal level prior to a substorm could be used for forecasting of space weather disturbed conditions.
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Somsikov, V. M., I. P. Chunchuzov, A. Jahanshir e S. N. Mukasheva. "SOLAR TERMINATOR AND IONOSPHERIC PROPAGATION OF RADIO WAVES". RADIO COMMUNICATION TECHNOLOGY, n. 51 (30 dicembre 2021): 15–23. http://dx.doi.org/10.33286/2075-8693-2021-51-15-23.
Testo completoAbstract (sommario):
The paper provides a review of studies devoted to the peculiarities of the propagation of radio waves in the ionosphere in the area of the solar terminator, which is the only global and regular source of acoustic-gravitational waves and other disturbances of the ionosphere. It describes the results of theoretical works devoted to the study of perturbations created by the solar terminator in the area of the difference in the intensity of solar radiation in the atmosphere. The paper gives a review of experimental studies of the effects created by the solar terminator in the entire thickness of the atmosphere. These effects, in particular, include the multipath propagation of radio waves, their phase variations, and variations in amplitudes during the propagation of radio waves in the area of the solar terminator. In the interests of science and practice, a number of problems have been proposed for the further study of wave perturbations arising as a result of the movement of the temperature gradient at sunrise and sunset hours.
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Kotik, Dmitriy, Ekaterina Orlova e Vladimir Yashnov. "Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma". Solnechno-Zemnaya Fizika 8, n. 4 (24 dicembre 2022): 57–65. http://dx.doi.org/10.12737/szf-84202205.
Testo completoAbstract (sommario):
We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.
26
Kotik, Dmitriy, Ekaterina Orlova e Vladimir Yashnov. "Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma". Solar-Terrestrial Physics 8, n. 4 (24 dicembre 2022): 55–62. http://dx.doi.org/10.12737/stp-84202205.
Testo completoAbstract (sommario):
We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.
27
Zernov, N. N., M. A. Bisyarin e V. E. Germ. "Diffraction Theory of Propagation of High-Frequency Radio Waves in a Spherically Layered Ionospheric Radio Channel". Радиотехника и электроника 68, n. 6 (1 giugno 2023): 563–70. http://dx.doi.org/10.31857/s0033849423060189.
Testo completoAbstract (sommario):
A special analytical method is developed to describe the propagation of high-frequency electromagnetic waves emitted by a vertical point dipole from the surface of perfectly conducting Earth in a regular spherically layered background ionosphere. The basic representation of the wave field employs an integral over the set of wave components, each of which is related to a specific ray trajectory. Such an approach makes it possible to analytically take into account the effect of medium-scale 3D inclusions in the background ionosphere as an additional phase shift of the wave component with allowance for the distortion of its ray trajectory and to numerically calculate the effect of wave-field focusing.
28
Afraimovich, E. L., N. P. Perevalova, A. V. Plotnikov e A. M. Uralov. "The shock-acoustic waves generated by earthquakes". Annales Geophysicae 19, n. 4 (30 aprile 2001): 395–409. http://dx.doi.org/10.5194/angeo-19-395-2001.
Testo completoAbstract (sommario):
Abstract. We investigate the form and dynamics of shock-acoustic waves generated by earthquakes. We use the method for detecting and locating the sources of ionospheric impulsive disturbances, based on using data from a global network of receivers of the GPS navigation system, and require no a priori information about the place and time of the associated effects. The practical implementation of the method is illustrated by a case study of earthquake effects in Turkey (17 August and 12 November 1999), in Southern Sumatra (4 June 2000), and off the coast of Central America (13 January 2001). It was found that in all instances the time period of the ionospheric response is 180–390 s, and the amplitude exceeds, by a factor of two as a minimum, the standard deviation of background fluctuations in total electron content in this range of periods under quiet and moderate geomagnetic conditions. The elevation of the wave vector varies through a range of 20–44°, and the phase velocity (1100–1300 m/s) approaches the sound velocity at the heights of the ionospheric F-region maximum. The calculated (by neglecting refraction corrections) location of the source roughly corresponds to the earthquake epicenter. Our data are consistent with the present views that shock-acoustic waves are caused by a piston-like movement of the Earth’s surface in the zone of an earthquake epicenter.Key words. Ionosphere (ionospheric disturbances; wave propagation) – Radio science (ionospheric propagation)
29
Xu, Xiang, Chen Zhou, Run Shi, Binbin Ni, Zhengyu Zhao e Yuannong Zhang. "Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes". Annales Geophysicae 34, n. 9 (21 settembre 2016): 815–29. http://dx.doi.org/10.5194/angeo-34-815-2016.
Testo completoAbstract (sommario):
Abstract. Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) model and the neutral atmosphere model (NRLMSISE-00), including the High Frequency Active Auroral Research Program (HAARP; 62.39° N, 145.15° W), Wuhan (30.52° N, 114.32° E) and Jicamarca (11.95° S, 76.87° W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.
30
Rapoport, Yuriy G., Oleg K. Cheremnykh, Volodymyr V. Koshovy, Mykola O. Melnik, Oleh L. Ivantyshyn, Roman T. Nogach, Yuriy A. Selivanov et al. "Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment". Annales Geophysicae 35, n. 1 (5 gennaio 2017): 53–70. http://dx.doi.org/10.5194/angeo-35-53-2017.
Testo completoAbstract (sommario):
Abstract. We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs), which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG) at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs) with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1). Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1) of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2) of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz) and VLF (kHz) ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system, measurements of electromagnetic and acoustic fields, study of the variations in ionospheric transparency for the radio emissions from galactic radio sources, optical measurements, and the impact on atmospheric aerosols. The proposed approach can be useful for better understanding the mechanism of the acoustic channel of seismo-ionospheric coupling.
31
Zhang, Y., e H. C. Wu. "Dispersive propagation of trans-ionospheric pulse pairs in ionosphere". AIP Advances 12, n. 5 (1 maggio 2022): 055126. http://dx.doi.org/10.1063/5.0087725.
Testo completoAbstract (sommario):
As the most powerful natural radio waves on earth, trans-ionospheric pulse pairs (TIPPs) are emitted by lightning and have been recorded by several satellites. TIPPs commonly consist of two radio pulses with a clear ionospheric dispersion. Here, we calculate the propagation of TIPPs across the ionosphere by use of a method accurate for sub-cycle radio pulses. One can directly obtain dispersed waveforms in the time domain and then reproduce satellite-recorded frequency spectra. Our work affords a simple and robust tool to directly compare with observation data, which should be helpful to deduce original undispersed waveforms of TIPPs and characteristics of high-energy electrons produced by lightning.
32
Dorogov, A. Yu, e A. I. Yashin. "SOFTWARE PACKAGE FOR MODELING HF-BAND PACKET RADIO NETWORKS". H&ES Research 12, n. 6 (2020): 26–37. http://dx.doi.org/10.36724/2409-5419-2020-12-6-26-37.
Testo completoAbstract (sommario):
It is noted that the complexity and constant variability of the ionosphere structure, the presence of many factors affecting the propagation of radio waves in such an environment, as well as the complex topology of communication networks lead to the need the computer modeling of data transmission in HF-band networks. The existing models of representation of ionospheric processes and digital radio channels are described. It is shown that to solve the problems of designing a radio data transmission network, complex modeling is necessary, taking into account the network topology, signal propagation losses in the radio channel, noise level, type of digital modulation, and radio forecast of communication conditions. In this paper, we consider a modeling complex for packet radio networks of HF-band data transmission with changing communication conditions. The complex consists of a set of interacting models implemented in the Matlab software environment. The software model for predicting communication conditions complies with ITU-R recommendation P. 533–13 of the International Telecommunication Union (ITU). The description of the model for the "Point-to-point" and "Area" modes is given and the results of its application for calculating extended radio lines are shown. The initial data and system parameters of the model are described. A model of the HF-band digital radio channel is presented. The communications System Toolbox package, which is part of the Matlab software environment, is used for this modeling. The model's input and output data are described. A model of Ionospheric Wave Frequency Dispatcher service of the radio network has been developed. This model is intended for building a wave schedule for stable operation of HF radio lines in the network. The rules for building a two-frequency and multi-frequency wave schedule are described. A scheme for modeling the operation of a packet radio network under changing communication conditions is proposed. The complex allows you to evaluate the probabilistic and temporal characteristics of radio lines and zonal radio coverage depending on geographical coordinates, time, month, solar activity and selected system parameters for a period of up to one year. Examples of using the modeling complex are given. The purpose of this work is to formulate the problem of simulation of HF radio networks under changing communication conditions.
33
Foroodi, Zahra, Mahdi Alizadeh, Harald Schuh e Lung-Chih Tsai. "Alternative Approach for Tsunami Early Warning Indicated by Gravity Wave Effects on Ionosphere". Remote Sensing 13, n. 11 (30 maggio 2021): 2150. http://dx.doi.org/10.3390/rs13112150.
Testo completoAbstract (sommario):
The rapid displacement of the ocean floor during large ocean earthquakes or volcanic eruptions causes the propagation of tsunami waves on the surface of the ocean, and consequently internal gravity waves (IGWs) in the atmosphere. IGWs pierce through the troposphere and into the ionospheric layer. In addition to transferring energy to the ionosphere, they cause significant variations in ionospheric parameters, so they have considerable effects on the propagation of radio waves through this dispersive medium. In this study, double-frequency measurements of the Global Positioning System (GPS) and ionosonde data were used to determine the ionospheric disturbances and irregularities in response to the tsunami induced by the 2011 Tohoku earthquake. The critical frequency of the F2 layer (foF2) data obtained from the ionosonde data also showed clear disturbances that were consistent with the GPS observations. IGWs and tsunami waves have similar propagation properties, and IGWs were detected about 25 min faster than tsunami waves in GPS ground stations at the United States west coast, located about 7900 km away from the tsunami’s epicenter. As IGWs have a high vertical propagation velocity, and propagate obliquely into the atmosphere, IGWs can also be used for tsunami early warning. To further investigate the spatial variation in ionospheric electron density (IED), ionospheric profiles from FORMOSAT-3/COSMIC (F3/C) satellites were investigated for both reference and observation periods. During the tsunami, the reduction in IED started from 200 km and continued up to 272 km altitude. The minimum observed reduction was 2.68 × 105 el/cm3, which has happened at 222 km altitude. The IED increased up to 767 km altitude continuously, such that the maximum increase was 3.77 × 105 el/cm3 at 355 km altitude.
34
Marshall, R. A., e F. W. Menk. "Observations of Pc 3-4 and Pi 2 geomagnetic pulsations in the low-latitude ionosphere". Annales Geophysicae 17, n. 11 (30 novembre 1999): 1397–410. http://dx.doi.org/10.1007/s00585-999-1397-2.
Testo completoAbstract (sommario):
Abstract. Day-time Pc 3–4 (~5–60 mHz) and night-time Pi 2 (~5–20 mHz) ULF waves propagating down through the ionosphere can cause oscillations in the Doppler shift of HF radio transmissions that are correlated with the magnetic pulsations recorded on the ground. In order to examine properties of these correlated signals, we conducted a joint HF Doppler/magnetometer experiment for two six-month intervals at a location near L = 1.8. The magnetic pulsations were best correlated with ionospheric oscillations from near the F region peak. The Doppler oscillations were in phase at two different altitudes, and their amplitude increased in proportion to the radio sounding frequency. The same results were obtained for the O- and X-mode radio signals. A surprising finding was a constant phase difference between the pulsations in the ionosphere and on the ground for all frequencies below the local field line resonance frequency, independent of season or local time. These observations have been compared with theoretical predictions of the amplitude and phase of ionospheric Doppler oscillations driven by downgoing Alfvén mode waves. Our results agree with these predictions at or very near the field line resonance frequency but not at other frequencies. We conclude that the majority of the observations, which are for pulsations below the resonant frequency, are associated with downgoing fast mode waves, and models of the wave-ionosphere interaction need to be modified accordingly.Key words. Ionosphere (ionosphere irregularities) · Magnetospheric physics (magnetosphere-ionosphere interactions) · Radio science (ionospheric physics)
35
Chisham, G., e M. Pinnock. "Assessing the contamination of SuperDARN global convection maps by non-F-region backscatter". Annales Geophysicae 20, n. 1 (31 gennaio 2002): 13–28. http://dx.doi.org/10.5194/angeo-20-13-2002.
Testo completoAbstract (sommario):
Abstract. Global convection mapping using line-of-sight Doppler velocity data from the Super Dual Auroral Radar Network (SuperDARN) is now an accepted method of imaging high-latitude ionospheric convection. This mapping process requires that the flow measured by the radars is defined solely by the convection electric field. This is generally only true of radar backscatter from the ionospheric F-region. We investigate the extent to which the E-region and ground backscatter in the SuperDARN data set may be misidentified as F-region backscatter, and assess the contamination of global convection maps which results from the addition of this non-F-region backscatter. We present examples which highlight the importance of identifying this contamination, especially with regard to the mesoscale structure in the convection maps.Key words. Ionosphere (plasma convection) – Radio science (radio wave propagation; instruments and techniques)
36
Gong, Hongwei, Hanxian Fang e Zeyun Li. "Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation". Universe 8, n. 6 (15 giugno 2022): 331. http://dx.doi.org/10.3390/universe8060331.
Testo completoAbstract (sommario):
In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital ray tracing technique. The results show that CO2 can effectively dissipate the background electrons and form ionospheric holes after being released in the ionosphere. At the peak height of ionospheric electron density (about 300 km), the electrons are dissipated fastest and the radius of ionospheric hole is also largest. This is due to the fact that the diffusion coefficient of CO2 usually increases with height while the electron density just increases before reaching its peak height and then decreases with height, and the chemical reaction rate between ions and CO2 also becomes largest at the peak height of electron density (about 300 km). Around 100 s after the release of CO2, when the radio waves at a frequency of 8 MHz pass through the ionosphere with an elevation range of 85~95°, the “secondary focusing effect” can occur, and we believe that this is due to the reflection of HF shortwaves on the walls of the ionospheric holes. With time going on, this phenomenon disappears at 300 s and only one focus is left at this time. For the HF shortwaves at same incident frequency, the focusing effect of waves displays a weakening trend with time increasing, and the height of focus center also ascends gradually. At the same time after CO2 releasing, with the increasing of radio waves frequency, the focusing effect also becomes weaker and the focus center displays an ascending trend.
37
Hughes, J. M., W. A. Bristow, R. A. Greenwald e R. J. Barnes. "Determining characteristics of HF communications links using SuperDARN". Annales Geophysicae 20, n. 7 (31 luglio 2002): 1023–30. http://dx.doi.org/10.5194/angeo-20-1023-2002.
Testo completoAbstract (sommario):
Abstract. Space weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radio waves propagate. Since many systems utilize HF communications, the ability to make real-time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper, we present new techniques for measuring high-latitude HF communications link parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequencies are estimated. These calculations are made in near-real-time and the results are made available on the World Wide Web. F-region critical frequencies calculated using this method show good agreement with ionosonde data.Key words. Ionosphere (active experiments; instruments and techniques) – Radio science (ionospheric propagation)
38
Chan, A. H. Y., e P. S. Cannon. "Nonlinear forecasts of ƒ<i>o</i>F2: variation of model predictive accuracy over time". Annales Geophysicae 20, n. 7 (31 luglio 2002): 1031–38. http://dx.doi.org/10.5194/angeo-20-1031-2002.
Testo completoAbstract (sommario):
Abstract. Space weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radio waves propagate. Since many systems utilize HF communications, the ability to make real-time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper, we present new techniques for measuring high-latitude HF communications link parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequencies are estimated. These calculations are made in near-real-time and the results are made available on the World Wide Web. F-region critical frequencies calculated using this method show good agreement with ionosonde data.Key words. Ionosphere (active experiments; instruments and techniques) – Radio science (ionospheric propagation)
39
Zhilinsky, Alexey P., e Vladimir F. Degtyarev. "TUNNEL BROADENING OF RESONANT LEVELS IN LAYERED QUANTUM-SIZE STRUCTURES". SYNCHROINFO JOURNAL 9, n. 1 (2023): 30–37. http://dx.doi.org/10.36724/2664-066x-2023-9-1-30-37.
Testo completoAbstract (sommario):
The microparticles interaction with potential barriers of various nature and form is the quantum physics and nanoelectronics basis. The nature of this interaction largely determines modern radio engineering devices and complexes operation, information transmission and processing systems. At present, semiconductor quantum-well structures, in particular heterostructures with quantum wells (QWs) and barriers (QWs), occupy leading positions as materials for opto- and nanoelectronics. It has been found that chain consisting of a sequence formation of potential wells and barriers gives rise to resonant levels for which the structure transparency is equal to unity. With an increase in the number of chain links, these levels split into close sublevels, the energy and half-width of which depend on the barriers parameters and the number of chain cells. A technique is proposed to determine the characteristics of these levels, in particular, the half-width of sublevels. The wave function dependence on chain parameters is studied. Problems related to the propagation of waves in layered media also arise in many other branches of science and technology. In particular, such media as plasma, ionosphere, atmosphere, ocean contain layered structures. Solving the problems of wave propagation in these media, calculating the reflection and transmission coefficients during the propagation of electromagnetic waves are of great importance both for calculating radio paths with reflection from the ionosphere and for many problems of remote diagnostics of ionospheric plasma. The issues discussed in this paper may be of interest to specialists in these areas.
40
Borisova, Tatiana, Nataly Blagoveshchenskaya, Alexey Kalishin e Andrey Kovalev. "Determination of the vector velocity of artificial ionospheric irregularities based on Doppler measurements by the bi-static scatter method of HF radio signals propagating over long radio paths". Solar-Terrestrial Physics 10, n. 2 (25 giugno 2024): 74–92. http://dx.doi.org/10.12737/stp-102202408.
Testo completoAbstract (sommario):
During experiments on the modification of the high-latitude ionosphere by high-power HF radio waves of ordinary or extraordinary polarization of the EISCAT/Heating facility (Tromsø, Norway) in 2013, 2016, and 2019, Doppler measurements of diagnostic HF radio signals over long radio paths were carried out by the bistatic scatter method. We studied characteristics of Doppler frequency variations in bistatic scattered radio signals, using the experimental results obtained along radio paths of different lengths (up to ~8500 km) and orientation. We examined numerical dependences of the Doppler frequency variations in a radio signal on the azimuth of the wave vector of a radio wave incident onto an artificially disturbed region, on the bistatic scattering angle, and on the azimuthal direction of irregularity motion in an artificially disturbed region of the ionosphere. From simultaneous measurements of the Doppler frequency fD of the radio signal along two diagnostic radio paths, we numerically estimated the velocity vector of irregularities in the artificially disturbed region of the ionosphere. The total vector velocity of artificial ionospheric irregularities can be calculated from measurements of the Doppler frequency shift along several long diagnostic radio paths after preliminary analysis of experimental observations with the results of trajectory modeling of diagnostic HF radio signals.
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Edwards, Danielle, e Manuel Cervera. "Seasonal Variation in Land and Sea Surface Backscatter Coefficients at High Frequencies". Remote Sensing 14, n. 21 (2 novembre 2022): 5514. http://dx.doi.org/10.3390/rs14215514.
Testo completoAbstract (sommario):
Over the horizon radars (OTHR) rely on the propagation of high frequency (HF) radio waves via the ionosphere to successfully achieve their designated missions. Backscatter sounders (BSS) are environmental over-the-horizon radars which may be used to assess the ionospheric propagation conditions. However, high power observed by a BSS may be due to either good ionospheric propagation, a high surface backscatter coefficient, or a combination of both. Hence, an understanding of the surface backscatter coefficients and their temporal variation is essential to fully understand the ionospheric propagation conditions. A database of surface backscatter coefficients over a decade was created using backscatter ionogram data from four backscatter sounders in Australia. The temporal variations in the backscatter coefficients were investigated and it was found that the land backscatter coefficients were relatively constant over time, while the sea backscatter coefficients showed significant seasonal variation.
42
Füllekrug, M., C. Hanuise e M. Parrot. "Simulating satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds". Atmospheric Chemistry and Physics Discussions 10, n. 10 (7 ottobre 2010): 23149–67. http://dx.doi.org/10.5194/acpd-10-23149-2010.
Testo completoAbstract (sommario):
Abstract. Relativistic electron beams above thunderclouds emit 100 kHz radio waves which illuminate the Earth's atmosphere and near-Earth space. This contribution aims to clarify the physical processes which are relevant for the spatial spreading of the radio wave energy below and above the ionosphere and thereby enables simulating satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds. The simulation uses the DEMETER satellite which observes 100 kHz radio waves from fifty terrestrial Long Range Aid to Navigation (LORAN) transmitters. Their mean luminosity patch in the plasmasphere is a circular area with a radius of 300 km and a power density of 22 μW/Hz as observed at 660km height above the ground. The luminosity patches exhibit a southward displacement of 450 km with respect to the locations of the LORAN transmitters. The displacement is reduced to 150 km when an upward propagation of the radio waves along the geomagnetic field line is assumed. This residual displacement indicates that the radio waves undergo 150 km sub-ionospheric propagation prior to entering a magnetospheric duct and escaping into near-Earth space. The residual displacement at low (L<2.14) and high (L>2.14) geomagnetic latitudes ranges from 100 km to 200 km which suggests that the smaller inclination of the geomagnetic field lines at low latitudes helps to trap the radio waves and to keep them in the magnetospheric duct. Diffuse luminosity areas are observed northward of the magnetic conjugate locations of LORAN transmitters at extremely low geomagnetic latitudes (L<1.36) in Southeast Asia. This result suggests that the propagation along the geomagnetic field lines results in a spatial spreading of the radio wave energy over distances of 1 Mm. The summative assessment of the electric field intensities measured in space show that nadir observations of terrestrial 100 kHz radio waves, e.g., from relativistic electron beams above thunderclouds, are attenuated by at least 50 dB when taking into account a transionospheric attenuation of 40 dB.
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Füllekrug, M., C. Hanuise e M. Parrot. "Experimental simulation of satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds". Atmospheric Chemistry and Physics 11, n. 2 (24 gennaio 2011): 667–73. http://dx.doi.org/10.5194/acp-11-667-2011.
Testo completoAbstract (sommario):
Abstract. Relativistic electron beams above thunderclouds emit 100 kHz radio waves which illuminate the Earth's atmosphere and near-Earth space. This contribution aims to clarify the physical processes which are relevant for the spatial spreading of the radio wave energy below and above the ionosphere and thereby enables an experimental simulation of satellite observations of 100 kHz radio waves from relativistic electron beams above thunderclouds. The simulation uses the DEMETER satellite which observes 100 kHz radio waves from fifty terrestrial Long Range Aid to Navigation (LORAN) transmitters. Their mean luminosity patch in the plasmasphere is a circular area with a radius of 300 km and a power density of 22 μW/Hz as observed at 660 km height above the ground. The luminosity patches exhibit a southward displacement of 450 km with respect to the locations of the LORAN transmitters. The displacement is reduced to 150 km when an upward propagation of the radio waves along the geomagnetic field line is assumed. This residual displacement indicates that the radio waves undergo 150 km sub-ionospheric propagation prior to entering a magnetospheric duct and escaping into near-Earth space. The residual displacement at low (L < 2.14) and high (L > 2.14) geomagnetic latitudes ranges from 100 km to 200 km which suggests that the smaller inclination of the geomagnetic field lines at low latitudes helps to trap the radio waves and to keep them in the magnetospheric duct. Diffuse luminosity areas are observed northward of the magnetic conjugate locations of LORAN transmitters at extremely low geomagnetic latitudes (L < 1.36) in Southeast Asia. This result suggests that the propagation along the geomagnetic field lines results in a spatial spreading of the radio wave energy over distances of 1 Mm. The summative assessment of the electric field intensities measured in space show that nadir observations of terrestrial 100 kHz radio waves, e.g., from relativistic electron beams above thunderclouds, are attenuated by at least 50 dB when taking into account a transionospheric attenuation of 40 dB.
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Pushin, V. F., e L. F. Chernogor. "A SYNTHESIS OF TEMPORAL VARIATIONS IN DOPPLER SPECTRA RECORDED AT A QUASI-VERTICAL INCIDENCE BY THE HF DOPPLER RADAR WITH SPACED RECEIVERS". Radio physics and radio astronomy 26, n. 3 (14 settembre 2021): 211–23. http://dx.doi.org/10.15407/rpra26.03.211.
Testo completoAbstract (sommario):
Purpose: The ionospheric channel is widely used for the communication, radio navigation, radar, direction finding, radio astronomy, and remote radio probing systems. The radio channel parameters are characterized by nonstationarity due to the dynamic processes in the ionosphere, and therefore their study is one of the topical problems of space radio physics and earth-space radio physics of geospace. This work aims at presenting the results of synthesis of temporal variations in the Doppler spectra obtained by the Doppler probing of the ionosphere at vertical and quasi-vertical incidence. Design/methotology/approach: One of the most effective methods of ionosphere research is the Doppler sounding technique. It has a high time resolution (about 10 s), a Doppler shift resolution (0.01–0.1 Hz), and the accuracy of Doppler shift measurements (~0.01 Hz) that permits monitoring the variations in the ionospheric electron density (10–4–10–3) or the study of the ionospheric plasma motion with the speed of 0.1-1 m/s and greater. The solution of the inverse radio physical problem, consisting in determination of the ionosphere parameters, often means solving the direct radio physical problem. In the Doppler sounding technique, it belongs with the construction of variations in Doppler spectra and comparing them with the Doppler spectra measurements. Findings: For the radio wave ordinary component, three echoes being produced by three rays are observed. Influence of the geomagnetic fi eld and large horizontal gradients in the electron density of δ≥10 % give rise to complex ray structures with caustic surfaces. The ionospheric disturbances traveling along the magnetic meridian form the skip zones. The longitudinal and transverse displacement of the ray reflection point attains a few tens of kilometers along the vil. Haidary to vil. Hrakove quasi-vertical radiowave propagation path, for which the great circle range is 50 km. For the vertical incidence, the signal azimuth at the receiver coincides with the traveling ionospheric disturbance azimuth. The synthesis of temporal variations in the HF Doppler spectra has been made and compared with the temporal variations in the Doppler spectra recorded with the V. N. Karazin Kharkiv National University radar. The estimate of δ=15 % obtained confirms the existence of large horizontal gradients in electron density. Conclusions: Temporal variations in Doppler spectra and in azimuth have been calculated for the vertical and quasi-vertical incidence with allowance for large horizontal gradients of the electron density caused by traveling ionospheric disturbances. Key words: ionosphere, Doppler sounding at oblique incidence, synthesis of temporal variations in HF Doppler spectra, traveling ionospheric disturbances, electron density
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Xu, Xin, Ling Huang, Shun Wang, Yicai Ji, Xiaojun Liu e Guangyou Fang. "VLF/LF Lightning Location Based on LWPC and IRI Models: A Quantitative Study". Remote Sensing 14, n. 22 (16 novembre 2022): 5784. http://dx.doi.org/10.3390/rs14225784.
Testo completoAbstract (sommario):
The group velocity of lightning electromagnetic signals plays an important role in lightning location systems using the time difference of arrival (TDOA) method. Accurate estimation of group velocity is difficult due to the space- and time-varying properties of the Earth’s ionospheric waveguide. Besides, the analytical solution of the group velocity is difficult to obtain from the classic mode theory, especially when higher-order modes, anisotropic geomagnetic background, diffuse ionosphere profile, and propagation path segmentation are all taken into consideration. To overcome these challenges, a novel numerical method is proposed in this paper to estimate the group velocity of the lightning signal during ionospheric quiet periods. The well-known Long Wavelength Propagation Capability (LWPC) code is used to model the propagation of VLF/LF radio waves. Since LWPC uses a simplified ionospheric model which is unable to describe the subtle variations of ionospheric parameters over time and space, the IRI-2016 model is incorporated into the numerical modeling process to provide more accurate ionosphere parameters. Experimental results of a VLF/LF lightning location network are demonstrated and analyzed to show the effectiveness of our method. The proposed method is also applicable when there is a sudden ionospheric disturbance as long as the parameters of the ionosphere are obtained in real time by remote sensing methods.
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Бернгардт, Олег, e Oleg Berngardt. "Space weather impact on radio device operation". Solar-Terrestrial Physics 3, n. 3 (9 ottobre 2017): 37–53. http://dx.doi.org/10.12737/stp-33201705.
Testo completoAbstract (sommario):
This paper reviews the space weather impact on operation of radio devices. The review is based on recently published papers, books, and strategic scientific plans of space weather investigations. The main attention is paid to ionospheric effects on propagation of radiowaves, basically short ones. Some examples of such effects are based on 2012–2016 ISTP SB RAS EKB radar data: attenuation of ground backscatter signals during solar flares, effects of traveling ionospheric disturbances of different scales in ground backscatter signals, effects of magnetospheric waves in ionospheric scatter signals.
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Witvliet, Ben A., Rosa M. Alsina-Pagès, Erik van Maanen e Geert Jan Laanstra. "Design and Validation of Probes and Sensors for the Characterization of Magneto-Ionic Radio Wave Propagation on Near Vertical Incidence Skywave Paths". Sensors 19, n. 11 (9 giugno 2019): 2616. http://dx.doi.org/10.3390/s19112616.
Testo completoAbstract (sommario):
This article describes the design and validation of deployable low-power probes and sensors to investigate the influence of the ionosphere and the Earth’s magnetic field on radio wave propagation below the plasma frequency of the ionosphere, known as Near Vertical Incidence Skywave (NVIS) propagation. The propagation of waves that are bent downward by the ionosphere is dominated by a bi-refractive mechanism called ‘magneto-ionic propagation’. The polarization of both downward waves depends on the spatial angle between the Earth’s magnetic field and the direction of propagation of the radio wave. The probes and sensors described in this article are needed to simultaneously investigate signal fading and polarization dynamics on six radio wave propagation paths. The 1-Watt probes realize a 57 dB signal-to-noise ratio. The probe polarization is controlled using direct digital synthesis and the cross-polarization is 25–35 dB. The intermodulation-free dynamic range of the sensor exceeds 100 dB. Measurement speed is 3000 samples/second. This publication covers design, practical realization and deployment issues. Research performed with these devices will be shared in subsequent publications.
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Zhbankov, G. A., e N. P. Danilkin. "INTERACTION OF SHORT-WAVE ELECTROMAGNETIC WAVES WITH SMALL-SCALE IONOSPHERIC INHOMOGENEITIES OF THE POLAR IONOSPHERE (part II)". RADIO COMMUNICATION TECHNOLOGY, n. 47 (23 novembre 2020): 45–56. http://dx.doi.org/10.33286/2075-8693-2020-47-45-56.
Testo completoAbstract (sommario):
The results of a comparative analysis of the data of computational and field experiments reflecting the peculiarities of the impact of small-scale inhomogeneities of electron concentration in the Earth's ionosphere on the characteristics of radio wave propagation during vertical ground-based and satellite sounding of the ionosphere are presented. It has been proved that these inhomogeneities are the cause of noticeable distortions of traces in ionograms. The simulation results confirm the possibility of determining the degree of concentration change in a small-scale inhomogeneous structure from experimental data.
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Jiang, Xiaoli, Huimin Li, Lixin Guo, Dalin Ye, Kehu Yang e Jiawen Li. "Research on the Ionospheric Delay of Long-Range Short-Wave Propagation Based on a Regression Analysis". Remote Sensing 16, n. 3 (31 gennaio 2024): 553. http://dx.doi.org/10.3390/rs16030553.
Testo completoAbstract (sommario):
The ionospheric delay effect is inevitable when a radio signal propagates through the ionosphere. It has been extensively studied in the L-band. Typically, the influence of the ionosphere on the code phase and carrier phase is regarded as the same. In this study, a numerical ratio between the group delay time and phase advance time with reference to the study of the L-band is investigated in the short-wave band. The variation in the numerical ratio with frequency, critical frequency, and elevation angle is discussed in detail. There appears an interesting phenomenon wherein the elevation angle has a greater effect on the ratio than the frequency and critical frequency. The numerical ratio increases with an increasing elevation angle. On the other hand, a regression analysis is used to establish the mapping relation between the ratio and the three factors of frequency, critical frequency, and elevation angle, based on the simulation results obtained by a ray-tracing algorithm. The little relative errors between the fitted values and simulation values under different ionospheric models prove the relationship between the ratio and the three factors of frequency, critical frequency, and elevation angle.
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Gauld, J. K., T. K. Yeoman, J. A. Davies, S. E. Milan e F. Honary. "SuperDARN radar HF propagation and absorption response to the substorm expansion phase". Annales Geophysicae 20, n. 10 (31 ottobre 2002): 1631–45. http://dx.doi.org/10.5194/angeo-20-1631-2002.
Testo completoAbstract (sommario):
Abstract. Coherent scatter HF ionospheric radar systems such as SuperDARN offer a powerful experimental technique for the investigation of the magnetospheric substorm. However, a common signature in the early expansion phase is a loss of HF backscatter, which has limited the utility of the radar systems in substorm research. Such data loss has generally been attributed to either HF absorption in the D-region ionosphere, or the consequence of regions of very low ionospheric electric field. Here observations from a well-instrumented isolated substorm which resulted in such a characteristic HF radar data loss are examined to explore the impact of the substorm expansion phase on the HF radar system. The radar response from the SuperDARN Hankasalmi system is interpreted in the context of data from the EIS-CAT incoherent scatter radar systems and the IRIS Riometer at Kilpisjarvi, along with calculations of HF absorption for both IRIS and Hankasalmi and ray-tracing simulations. Such a study offers an explanation of the physical mechanisms behind the HF radar data loss phenomenon. It is found that, at least for the case study presented, the major cause of data loss is not HF absorption, but changes in HF propagation conditions. These result in the loss of many propagation paths for radar backscatter, but also the creation of some new, viable propagation paths. The implications for the use of the characteristics of the data loss as a diagnostic of the substorm process, HF communications channels, and possible radar operational strategies which might mitigate the level of HF radar data loss, are discussed.Key words. Ionosphere (ionosphere-magnetosphere interactions). Magnetospheric physics (storms and substorms). Radio science (radio wave propagation)