The electron density profile inversion for incompletely developed case of F1 layer
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摘要: 垂测电离图反演对研究电离层结构及运动、电离层波传播、空间气象应用等具有重要意义,一直以来受到十分广泛的重视.F1层未充分发展的回波描迹是垂测电离图中观测到的最多的一种情况,此时垂测描迹上表现为F1层到F2层的平滑过渡,而不是F1层充分发展时出现的尖点,然而现有电离层模型以及反演算法更多的是针对F1层充分发展情况,即模型剖面在F1层峰高处近似为抛物形状,此处电子浓度剖面梯度为无穷大,这不符合F1层未充分发展时的剖面形态,即F1层剖面未到达抛物顶点处就已经达到该层电子浓度的最大值然后到达F2层,剖面梯度为一个有限的数值.因此,本文针对垂直探测中经常出现的F1层未充分发展情况,引入F1层模型设定临频这一参数,建立了F1层未充分发展时的基于移位切比雪夫多项式的电离层模型,并从电离层剖面的光滑性考虑,在所建模型的基础上,提出了约束优化F1层参数、F2层参数的垂测电离图反演方法.然后,通过仿真分析,从理论上验证了所建电离层模型和反演算法的合理性,并通过反演电子浓度剖面合成的垂测、斜测描迹与实测数据的对比,对反演算法的有效性进行了进一步的试验验证.Abstract: The electron density profile inversion from vertical incidence ionograms, which is essential for research in ionospheric structures and movements, wave propagation and space weather applications, has gathered very wide attention. The echo trace of incompletely developed F1 layer is common in vertical incidence ionograms, and it is usually expressed as smooth transition from F1 layer to F2 layer, not a cusp appeared at the critical frequency of F1 layer. However, the existing ionospheric models and inversion algorithms are generally intended for the completely developed F1 layer with the assumptions of a parabolic profile and an infinite slope at the peak of F1 layer, which are not suitable for the profile of incompletely developed F1 layer which achieves the maximum electron density of F1 layer and enters F2 layer at the peak of F1 layer and has a finite slope. Consequently, a F1 layer electron density profile model based on the shifted Chebyshev polynomial for incompletely developed case of F1 layer is introduced with a parameter named model setting critical frenquency. Taking into account the profile smoothness, an electron density profile inversion algorithm with constrained optimization F1 and F2 layer parameters based on the model mentioned above is proposed. The validity of the model and the inversion algorithm is analyzed through the simulation, and the effectivity of the proposed algorithm is further verified by the comparison between the synthesized vertical sounding & oblique sounding traces and the measured data.
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Key words:
- F1 layer /
- Incompletely developed /
- Inversion /
- Ionosphere profile /
- Vertical sounding
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