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5~10dB,但其散射覆盖区的地面范围大,东西向可达3000km,南北向可达1500km,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.
Ionospheric heating experiments using powerful,high frequency（HF）radio waves have been performed at many locations throughout the world since the early 1970 s.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-alignedscattering（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 108 m2 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
作者
吕立斌
李清亮
郝书吉
吴振森
LU LiBin;LI QingLiang;HAO ShuJi;WU ZhenSen(School of Physics and Optoelectronic Engineering, Xidian University, Xi＇an 710071, China;China Research Institute of Radiowave Propagation, National Key Laboratory of Electromagnetic Environment, Qingdao 266107, China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第6期2177-2185,共9页
Chinese Journal of Geophysics
基金
中国电科技术创新基金(KJ1602004)资助
