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In this study, associating with the A‐H formulation, we have developed a comprehensive ionospheric absorption model by incorporating the latest version of geomagnetic model, the atmospheric and ionospheric model as the background. Based on the absorption model, the ionospheric stratification theory is utilized to explore the trend of the total absorption for extraordinary (X) wave with frequency and elevation angle. We found that the factor of local time has a greater impact on the trend of total absorption variation than other factors—solar activity, season, and latitude, attributing to the variation of electron collision frequency. During the two different local times (daytime and night), the trends of the total absorption have distinct differences. In the daytime, it is worth noting that the reflection heights and the peaks of the absorption coefficient both mainly occur in Layers D and E. Therefore, the non‐deviative absorption dominates the variation of the total absorption. On the other hand, the occurrence of Pedersen ray results in inflexion points arising in the curves of absorption versus frequency or elevation angle. Another interesting phenomenon is the dominant role of deviative absorption at night. At night, the reflection heights mainly occur in Layer F, and the absorption coefficient of Layer F begins to exceed the peak levels of Layers D and E when the frequency or elevation angle is larger than certain values. Hence, the total absorption will grow as a result of the increase in deviative absorption with the increase in reflection height and absorption coefficient. Key Points: The greater difference of trend of total absorption variation occurs in the diurnal cycle than that in solar activity, season, and latitude, attributing to the variation of electron collision frequencyIn daytime, the non‐deviative absorption dominates the trend of the total absorption, while at night, the deviative absorption plays a dominant role at the high frequency or high elevation angle (when the frequency or elevation angle are larger than the certain values)The occurrence of Pedersen ray results in inflection points arising in the curves of absorption versus frequency or elevation angle [ABSTRACT FROM AUTHOR]

The consequences are studied of the localization effect of ion Bernstein (IB) waves excited in secondary decay processes accompanying the development of low-threshold parametric decay instability of the extraordinary pump wave, which results in the excitation of the extraordinary wave and the upper-hybrid (UH) wave localized in the plasma. It is shown that in experiments on electron cyclotron resonance plasma heating at the second resonance harmonic, the effect discovered results in a decrease in both the saturation level of primary instability and anomalous absorption level of the pump wave. [ABSTRACT FROM AUTHOR]

Abstract The most important aim in interpreting an oblique ionogram is to obtain the accurate Junction Frequencies (JFs) of the ordinary (O) and extraordinary (X) mode. This requires the correct identification of O- and X-mode traces, so it is very helpful and worthy to grasp the relative position between the two modes. This paper presents a statistical and simulation study of the separation in JFs between O- and X-waves based on observed oblique ionograms over three mid-latitude paths within China and a 3D ray-tracing program. The dependence on local time, season, geomagnetic activity, O-wave JF and group path, solar activity, direction, and length of propagation is investigated. The main conclusions are as follows: (a) the separation on east–west path is susceptible to ionospheric variability, while the separation on north–south path does not show a significant correlation with local time and season; (b) a general diurnal tendency and a summer anomaly on east–west propagation are first proposed and discussed, which may be related to the diurnal variation of hmF2 above the reflection point and the strong lower layers below the reflection point; (c) the separation varies approximately as a cosine function with the propagation direction owning two maxima in the north–south direction and two minima in the east–west direction; (d) the variation patterns of the separation with the propagation length are obviously not the same in different directions. In the case of east–west propagation, the separation decreases to a minimum near ground range of 2000 km and then increases very slowly with increasing ground range, while it monotonically increases for the north–south propagation path. Graphical Abstract

The most important aim in interpreting an oblique ionogram is to obtain the accurate Junction Frequencies (JFs) of the ordinary (O) and extraordinary (X) mode. This requires the correct identification of O- and X-mode traces, so it is very helpful and worthy to grasp the relative position between the two modes. This paper presents a statistical and simulation study of the separation in JFs between O- and X-waves based on observed oblique ionograms over three mid-latitude paths within China and a 3D ray-tracing program. The dependence on local time, season, geomagnetic activity, O-wave JF and group path, solar activity, direction, and length of propagation is investigated. The main conclusions are as follows: (a) the separation on east–west path is susceptible to ionospheric variability, while the separation on north–south path does not show a significant correlation with local time and season; (b) a general diurnal tendency and a summer anomaly on east–west propagation are first proposed and discussed, which may be related to the diurnal variation of hmF2 above the reflection point and the strong lower layers below the reflection point; (c) the separation varies approximately as a cosine function with the propagation direction owning two maxima in the north–south direction and two minima in the east–west direction; (d) the variation patterns of the separation with the propagation length are obviously not the same in different directions. In the case of east–west propagation, the separation decreases to a minimum near ground range of 2000 km and then increases very slowly with increasing ground range, while it monotonically increases for the north–south propagation path. [ABSTRACT FROM AUTHOR]

The excitation of upper‐hybrid wake electrostatic wave by interaction of an extraordinary Gaussian wave propagating perpendicular to the external magnetic field in a cold homogeneous plasma is investigated using magnetohydrodynamics theory. The plasma oscillations can be excited due to the charge separation appeared by the ponderomotive force of the electromagnetic wave whose frequency is considered in the lower pass band. By obtaining the equation governing the plasma wake, the dependency of the wake amplitude on the physical parameters is studied. It is observed that larger wake oscillation takes place when the pulse length is approximately close to 3λp/π and the X‐wave frequency is greater than ωp, which means that the phase velocity is less than the speed of light in vacuum (vp < c). [ABSTRACT FROM AUTHOR]

Ray tracing theory for a radially uniaxial dielectric sphere is presented in this communication. Reflection and transmission of the plane waves obliquely incident on the spherical interface between air and uniaxial are briefly examined and the general formulations for phase velocities as well as the refractive indices of the ordinary and extraordinary waves propagating in a radially uniaxial medium are investigated. The ray tracing method is implemented for both ordinary and extraordinary rays and the results are applied to evaluate the propagation paths and arrival times of the shortcut wave returns appearing in the transient backscattering response of a uniaxial dielectric sphere. The effect of the variation in relative permittivity on the arrival times of shortcut waves is studied. The results of the ray tracing method are compared with those computed using the Mie and Debye series solutions with good agreement. [ABSTRACT FROM PUBLISHER]

Abstract: The anisotropy of the near-bandgap absorption is investigated in AgAsS2 crystals. The refraction indices, n ‖ and n ⊥ respectively for the E‖c and E⊥c polarizations as well as the spectral dependence of the refraction indices difference, Δn=n‖−n ⊥ are determined from the interference spectra of AgAsS2 crystals. A transmission band with four maxima is observed in the transmission spectra of crystals placed between crossed polarizers. The optical parameters n, k, ε 1, and ε 2 for the E‖c and E⊥c polarizations are calculated from the reflection spectra by using the Kramers–Kronig relations. [Copyright &y& Elsevier]