A ray‐tracing model to account for off–great circle HF propagation over northerly paths
A ray‐tracing model to account for off–great circle HF propagation over northerly paths
复制标题
用于解释北向路径上的离大圆高频传播的射线追踪模型
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
A. Stocker
中科院分区：
文献类型：
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作者：
N. Zaalov;E. M. Warrington;A. Stocker
离大圆HF传播效应是北半球电离层（即亚极光槽区、极光带和极帽）的共同特征。除了它们在偏离大圆路径可能导致显著三角测量误差的无线电定位应用中的重要性外，它们在另外两个方面也很重要：(1)在采用沿大圆路径指向的定向天线的系统中，当传播通过非大圆传播模式时，信号质量有时可能会下降；(2)非大圆传播机制可能导致信号频率超过沿大圆路径的最大可用频率时传播。本文描述了一种覆盖北半球电离层的射线追踪模型。使用该模型得到的结果与在各种实验测量程序中观察到的方向特性非常相似，因此，相信该模型可以用于估计未受实验研究的路径的离大圆传播效应的性质。虽然不可能预测个别的非大圆传播事件，但可以预测可能发生大偏差的周期及其幅度和方向。
Off–great circle HF propagation effects are a common feature of the northerly ionosphere (i.e., the subauroral trough region, the auroral zone, and the polar cap). In addition to their importance in radiolocation applications where deviations from the great circle path may result in significant triangulation errors, they are also important in two other respects: (1) In systems employing directional antennas pointed along the great circle path, the signal quality may be degraded at times when propagation is via off–great circle propagation modes; and (2) the off–great circle propagation mechanisms may result in propagation at times when the signal frequency exceeds the maximum usable frequency along the great circle path. A ray‐tracing model covering the northerly ionosphere is described in this paper. The results obtained using the model are very reminiscent of the directional characteristics observed in various experimental measurement programs, and consequently, it is believed that the model may be employed to enable the nature of off–great circle propagation effects to be estimated for paths which were not subject to experimental investigation. Although it is not possible to predict individual off–great circle propagation events, it is possible to predict the periods during which large deviations are likely to occur and their magnitudes and directions.