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The sporadic E‐layer (Es) exhibits unique opportunity for exploring the coupling from lower to upper atmosphere. It was found that the East Asia is with the highest intensity and occurrence probability of Es. By using the long‐term data of 21 ionosonde stations in China and Japan over the past 60 yrs, this paper explores the probable control on the Es layer from the lower layers. It is found that the intensity of the Es layer is strongly correlated with the surface atmospheric temperature, terrain, and land‐sea boundary. The correlation coefficient of the intensity of Es with surface temperature is as high as 0.8204, while that with the terrain and land‐sea boundary is up to 0.6668. Based on the coupling between the lower and upper atmosphere, this paper reveals the probable controls from lower layers on the intensity of the Es in East Asia. Plain Language Summary: As an occasional ionized layer of the ionosphere, the sporadic E‐layer (Es) exhibits unique opportunity for exploring the coupling from lower to upper atmosphere. Despite extensive research on both behavior and mechanism of the Es, none have adequately explained the strong inhomogeneous of its global morphology. It is found in fact that the East Asia is with the highest intensity and occurrence probability of Es. By using the long‐term data of 21 ionosondes in China and Japan over the past 60 yrs, this letter explores the formation mechanism of the strongest Es regions in the world. It is found that the intensity of the Es layer is strongly correlated with the surface atmospheric temperature, terrain, and land‐sea boundary. The correlation coefficient between the intensity of Es and surface temperature is highest, while that with the terrain and land‐sea boundary is also high. By analyzing the data as long as six decades, this letter reveals the probable controls from lower layers on the intensity of the Es in East Asia. Key Points: By analyzing the six‐decade data of 21 ionosondes in East Asia, it reveals probable controls on the strongest Es layer from lower layersFor the first time, it is found that the intensity of Es layer is highly correlated with the surface atmospheric temperatureAn interesting coupling from lower to upper atmosphere may be found by taking advantage of observations longer than half of a century [ABSTRACT FROM AUTHOR]

On the basis of a solution to the mutual coherence function (MCF) obtained recently, this paper investigates the characteristics of pulse propagation through the turbulent ionosphere in arbitrary scattering regimes. First, the MCF is numerically discussed using different spectra of irregularities with different frequencies, bandwidths, and fluctuation regimes. Second, the mean arrival time of a pulse through the turbulent ionosphere is investigated. The dominant term is the travel time at the group velocity. Other effects are mainly from the higher order dispersion of background and scattering of irregularities, while the dispersion of irregularities is relatively small and can be neglected. It is found that effects from the scattering and dispersion of irregularities to the excess time delay decrease with increasing of the spectral index, the outer and inner scale, while increase quickly with fluctuations. Index Terms--Electromagnetic propagation in random media, electromagnetic scattering by random media, ionospheric electromagnetic propagation, pulse propagation.

There has been a considerable interest in the use of lower frequency (VHF/UHF) space-based synthetic aperture radar (SAR) for realizing the foliage and ground penetration. The phase perturbation, signal distortion and imaging resolution degradation by the ionosphere will be particularly severe, however the model is not yet well established and still needs to be further studied. In this paper, on the basis of possible improvements for the model proposed by Ishimaru and others, potential ionospheric effects on SAR imaging are evaluated. First, for analyzing azimuthal resolution, we apply the fourth moment recently obtained in general case of strong fluctuation regimes, which is expected to give results for wider conditions. The Gaussian approximation was used in the previous model: however it is only valid in the fully saturated regimes. Second, for analyzing image shift and distortion, besides group delay, the higher-order dispersion is considered. Third, for discussing range resolution degraded due to pulse broadening, besides the dispersion, the multiple scattering of ionospheric turbulence is studied. Fourth, the Faraday rotation effect is analyzed. Numerical simulations are shown using ionospheric turbulence spectrum and TEC inferred from the International Reference Ionosphere (IRI) and satellite beacon observations. Index Terms--Electromagnetic propagation in random media, ionospheric electromagnetic propagation, synthetic aperture radar (SAR).

The fourth moment plays an important role in wave propagation and scattering in random media. However, in the strong scattering regimes, it remains to be solved although a rich variety of methods have been proposed. The fourth moment equation is solved using the modified Gaussian solution method proposed in this paper. The fourth moment can be considered as a sum of the Gaussian solution and non-Gaussian correction term. The Gaussian solution is the fourth moment in the saturated regime, and can be obtained as a sum of products of the second-order moments. The derived equation of the non-Gaussian correction term is solved using the Rytov approximation and the Green's function. The fourth moment solution obtained is general for without restrictions on incident wave forms. Specifically, the solution for a plane wave is derived and applied to study the amplitude scintillation and intensity correlation function of transionospheric radio signals. The theoretical calculation on the scintillation index agrees well with the experimental results, which confirms the fourth moment solution to some extent. Index Terms--Electromagnetic propagation in random media, electromagnetic scattering by random media, ionospheric electromagnetic propagation, ionospheric scintillation.

Higher order symmetrical moments play an important role in wave propagation and scattering in random media, however it remains to be solved under strong fluctuations. In this paper, a modified Gaussian solution method is proposed for analytically solving the n-nth moment. After propagating through a random medium in the fully saturated regime, the higher order symmetrical moment of the received wave is the sum of products of the second moments, i.e., the Gaussian solution. In strong scattering regimes, the higher order symmetrical moment can be considered as a sum of the Gaussian solution and a non-Gaussian correction term, where the key issue is how to solve the derived equation of the correction term. Two methods are proposed, i.e., Green's function method and the Rytov approximation approach. Green's function method leads to a rigorous solution form, but it is complicated due to an integral equation. The approach using the Rytov approximation is found to be reasonable, as the correction is relatively small. Index Terms--Electromagnetic propagation in random media, electromagnetic scattering by random media, ionospheric electromagnetic propagation.

Training independent innovative ability for undergraduates is an important task of the modern higher education. Training mode of the independent innovative ability is an important subject of university teachers. A training mechanism of "coupling of commonalities and characteristics" and a process mode of multidimensional roundabout experimental innovation were proposed in this work. Stimulation of innovative consciousness, cultivation of innovative thinking, building-up of innovative spirit and attention of innovative practice process were set up in the mechanism and the mode. The independent innovative ability of undergraduates had been successfully trained and promoted. [ABSTRACT FROM AUTHOR]