| 大功率高频电波加热电离层中人工沿场不均匀体散射特性的理论与数值模拟研究 |
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| 引用本文： | 吕立斌,李清亮,郝书吉,吴振森.大功率高频电波加热电离层中人工沿场不均匀体散射特性的理论与数值模拟研究[J].地球物理学报,2018,61(6):2177-2185. |
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| 作者姓名： | 吕立斌 李清亮 郝书吉 吴振森 |
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| 作者单位： | 1. 西安电子科技大学物理与光电工程学院, 西安 710071;
2. 中国电波传播研究所, 电波环境特性及模化技术重点实验室, 青岛 266107 |
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| 基金项目： | 中国电科技术创新基金（KJ1602004）资助. |
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| 摘 要： | 大功率高频电波与电离层的相互作用会引起电子密度扰动，进而产生人工沿场不均匀体，其对无线电波特别是超短波信号有强的定向散射能力，可形成一种新型的超短波通信方式.基于各向异性介质的散射理论，首先通过求解电子密度扰动产生的附加极化势获得电子密度扰动散射方程，然后对电子密度扰动进行高斯自相关处理，并结合入射波/散射波与地磁场方向的空间几何关系，获得电子密度扰动的波数谱表达式，建立了人工沿场不均匀体的散射系数理论模型.利用模型对Platteville站实验中产生的人工不均匀体散射截面积进行了数值模拟，并通过与实测值对比验证了模型的正确性.根据人工沿场散射原理给出了利用其进行无线电信号传输的约束条件.重点仿真分析了人工沿场不均匀体的散射系数和散射覆盖区范围，结果表明：同等条件下，相对于高纬度地区，低纬度地区人工沿场不均匀体的散射系数小5~10 dB，但其散射覆盖区的地面范围大，东西向可达3000 km，南北向可达1500 km，完全可用于超短波信号的超远距离传输.本文结果为中低纬度地区开展相关实验研究提供了理论指导，对利用人工沿场不均匀体进行无线信号的超远距离传输应用研究具有重要意义.
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| 关 键 词： | 大功率高频电波 人工沿场不均匀体 散射系数 超短波通信 |
| 收稿时间： | 2017-11-13 |
Study on scattering characteristic of AFAI in ionospheric heating by powerful high frequency waves |
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| LÜ,LiBin,LI QingLiang,HAO ShuJi,WU ZhenSen.Study on scattering characteristic of AFAI in ionospheric heating by powerful high frequency waves[J].Chinese Journal of Geophysics,2018,61(6):2177-2185. |
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| Authors: | LÜ LiBin LI QingLiang HAO ShuJi WU ZhenSen |
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| Institution: | 1. School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, China;
2. China Research Institute of Radiowave Propagation, National Key Laboratory of Electromagnetic Environment, Qingdao 266107, China |
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| Abstract: | Ionospheric heating experiments using powerful, high frequency (HF) radio waves have been performed at many locations throughout the world since the early 1970s. A large number of interesting phenomena have been observed, with indications of potential applications in radio wave propagations. One of the most interesting effects is the generation of artificial field-aligned irregularities (AFAI), with elongated electron density fluctuation structures aligned to the geomagnetic field. Due to their particular field-aligned structures, AFAI can scatter radio waves in a cone with its axis parallel to the geomagnetic field, which is known as artificial field-aligned scattering (AFAS). An important potential application of AFAI is to establish long-distance communication circuits. Such experiments have been carried out in Platteville between 1970 and 1974. The appearance of artificial spread F provides some evidences for formations of AFAI, which have been directly verified by observations using HF and very high frequency (VHF) radars afterwards. The artificial scatter has huge cross sections up to 108m2 and can be used for information transmissions upon several long-distance communication circuits. However, due to influences of ionosphere background conditions and the geomagnetic field, the scattering abilities of AFAI are quite distinctive for different latitudes. Based on the scattering theory of anisotropic irregularities, the scattering equations of electron density fluctuations have been derived in this paper, with assumptions of a Gaussian autocorrelation function. Using the geometry relation among the incident/scattering waves and the geomagnetic field, the wave number spectrum of electron density fluctuations has been obtained, and then a theoretical model of scattering coefficients has been constructed.
For cross sections of AFAI generated in the experiment at Platteville, the calculations are consistent with experimental measurements, which verify our model. Moreover, the constraint conditions have been obtained with the AFAS model for wireless transmission with AFAI. With the model, variances of scattering coefficients with the geomagnetic field, effective radiated power (ERP), and frequency have been simulated. It is shown that scattering coefficients are larger at high latitudes than those at mid and low latitudes for the same conditions. The values at Platteville and HAARP are about 5 dB larger than those at Wuhan and 10 dB larger than those at Guangzhou when ERP is 100 MW. Besides, due to special structures of AFAI, AFAS has extremely high aspect sensitivity, and the scattering coverage becomes smaller at high-latitudes. The calculations in this paper show a distinct advantage at mid and low latitudes, which may give a possible explanation upon the fact that there are almost no such experimental reports for HAARP. Based on our simulation, with an ERP exceeds 250 MW at Wuhan or 650 MW at Guangzhou, the scattering coefficients will have equivalent magnitudes with those at Platteville, which can support VHF transmission on long-distance circuits. |
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| Keywords: | Powerful high frequency waves AFAI Scattering coefficient VHF communication |
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