Ionospheric irregularity diagnostics from the phase structure functions of MF/HF radio echoes
Ionospheric irregularity diagnostics from the phase structure functions of MF/HF radio echoes
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根据 MF/HF 无线电回波的相位结构函数诊断电离层不规则性
DOI：
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发表时间：
2001
期刊：
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通讯作者：
J. Wright
中科院分区：
文献类型：
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作者：
N. Zabotin;J. Wright
我们提出了一种新的方法来调查电离层的不规则性，使用全反射无线电回波相位变化的时间结构函数。现代数字电离层探测仪（例如，dynasonde）以非常高的分辨率和精确度，以紧密间隔的天线、频率和时间测量回波相位。一个“串”的程序给出了连续和明确的相位变化数据的时间间隔的任何所需的长度。几十秒到几分钟的准周期是由电离层等离子体的大尺度运动引起的，而较短周期的相位变化是由探测信号与小尺度不规则性的相互作用引起的。相关的不规则空间域从10分之一无线电波长延伸到第一菲涅尔尺度，几公里。通过一个简单的冻结水平漂移模型，我们得到了时间相位变化和空间不规则性结构函数之间的理论关系。该关系允许的正问题和反问题的解决方案。虽然长周期相位测量对于探索更大的不规则尺度是可行的和必不可少的，但它们需要专用于多个固定频率时间序列的观测模式，这不期望地限制了可以同时监测的高度的数量。另一种“基本结构函数”可从标准动力测风仪“B‐模式”电离图获得;它为不规则性研究提供了良好的高度和时间分辨率，同时允许其他已建立的诊断（电子密度剖面、矢量速度、临界频率等）。相同的数据。我们展示了一些应用于极光和磁赤道动态探空仪观测的实例分析。我们发现不规则振幅在0.001 < ΔN/N < 0.1的范围内（对于1 km的标称尺度），光谱指数在2 < v < 4的范围内，两个位置的两个量都有日变化的证据。
We present a new approach to investigating ionospheric irregularities, using the temporal structure function of totally reflected radio echo phase variations. Modern digital ionosondes (e.g., the dynasonde) measure the echo phase with very high resolution and precision, at closely spaced antennas, frequencies, and times. A “stringing” procedure gives continuous and unambiguous phase variation data for time intervals of any desired length. Quasi‐periods of tens of seconds up through several minutes are caused by large‐scale movements of the ionospheric plasma, while shorter‐period phase variations result from the interaction of the sounding signal with small‐scale irregularities. The relevant irregularity spatial domain extends from decameter radio wavelengths to the first Fresnel scale, a few kilometers. We obtain a theoretical relation between structure functions of the temporal phase variations and spatial irregularities with a simple model of frozen horizontal drift. The relation permits solutions of both the direct and inverse problems. Although long‐period phase measurements are practicable and essential to exploring larger irregularity scales, they require observing modes dedicated to multiple fixed‐frequency time series, and this undesirably limits the number of altitudes that can be monitored simultaneously. An alternative “rudimentary structure function” is obtainable from standard dynasonde “B‐mode” ionograms; it offers good altitude and time resolution for irregularity studies while permitting other established diagnostics (electron density profiles, vector velocities, critical frequencies, etc.) with the same data. We show some example analyses by these methods as applied to auroral and magnetic‐equatorial dynasonde observations. We find irregularity amplitudes in the range 0.001 < ΔN/N < 0.1 (for a nominal scale of 1 km) and spectral indices in the range 2 < v < 4, with evidence of diurnal variation in both quantities at both locations.