On the Relationship Between the Rate of Change of Total Electron Content Index (ROTI), Irregularity Strength (CkL), and the Scintillation Index (S4)
On the Relationship Between the Rate of Change of Total Electron Content Index (ROTI), Irregularity Strength (CkL), and the Scintillation Index (S4)
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DOI：
10.1029/2018ja026353
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发表时间：
2019-03-01
影响因子：
2.8
通讯作者：
Rino, Charles L.
中科院分区：
文献类型：
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作者：
Carrano, Charles S.;Groves, Keith M.;Rino, Charles L.
我们通过注意到总电子含量指数（ROTI）与电离层湍流相结构函数的直接关系，提出了一种新的定量理论。该理论提供了ROTI与采样间隔、卫星运动、传播几何形状以及不规则性的光谱形状、强度、各向异性和漂移的依赖关系。我们还提出了阐明主要依赖关系的完整理论的有用近似。例如，我们表明，ROTI随有效扫描速度（V-eff）的幂（nu - 1/2）而变化，其中2 nu + 1是三维不规则性的光谱指数。这种对V-eff的依赖存在于ROTI与闪烁强度指数（S-4）的比值中，因此这取决于每颗卫星的特定观测几何形状。虽然不规则强度在形成这一比率时被抵消，但对菲涅耳比例尺的依赖仍然存在。我们通过比较1 hz ROTI测量的不规则强度（CkL）和S-4的预测结果与在阿森松岛收集的20 hz强度样本的计算结果，验证了这一理论。该理论很好地解释了观测结果，除了扫描几乎沿着场对准的不规则方向（在子午线20度以内）。对于交叉场扫描，1 hz ROTI预测弱、中、强闪烁的S-4误差的标准差分别为0.05、0.11和0.14。这些令人鼓舞的结果表明，使用廉价的总电子含量监测仪的密集网络来提供电离层闪烁和引起它们的不规则性的定量诊断的可能性。我们提出了一个新的理论模型，将广泛使用的总电子含量波动的统计测量与电离层不规则性及其产生的闪烁的统计测量联系起来。该模型包括以前未定量考虑的几种影响，包括采样间隔、卫星运动、传播几何形状、频谱形状、强度、各向异性和磁场对齐电离层不规则漂移。我们利用在阿森松岛，一个赤道站，在太阳极大期收集的测量数据验证了这一理论。
We present a new quantitative theory for the rate of change of total electron content index (ROTI) by noting its straightforward relationship to the phase structure function of ionospheric turbulence. The theory provides the dependence of ROTI on the sampling interval, satellite motion, propagation geometry, and the spectral shape, strength, anisotropy, and drift of the irregularities. We also present useful approximations to the full theory that elucidate the principal dependencies. We show, for example, that ROTI varies with the effective scan velocity (V-eff) to the power nu - 1/2, where 2 nu + 1 is the spectral index of the 3-D irregularities. This dependence on V-eff persists in the ratio of ROTI to the intensity scintillation index (S-4), which thus depends on the particular viewing geometry for each satellite. While irregularity strength cancels when forming this ratio, the dependence on Fresnel scale remains. We validate the theory by comparing predictions of irregularity strength (CkL) and S-4 from 1-Hz ROTI measurements with calculations derived from 20-Hz intensity samples collected at Ascension Island. The theory explains the observations well, except when the scan is directed nearly along the field-aligned irregularities (within 20 degrees of meridional). For cross-field scans the standard deviations of the error in predicting S-4 from 1-Hz ROTI were 0.05, 0.11, and 0.14 for weak, moderate, and strong scintillation, respectively. These encouraging results suggest the possibility of using dense networks of inexpensive total electron content monitors to provide quantitative diagnostics of ionospheric scintillation and the irregularities that cause them.Plain Language Summary We present a new theoretical model to relate a widely used statistical measure of fluctuations in total electron content to statistical measures of ionospheric irregularities and the scintillations they produce. This model includes several effects not previously accounted for quantitatively, including the sampling interval, satellite motion, propagation geometry, and the spectral shape, strength, anisotropy, and drift of magnetic field-aligned ionospheric irregularities. We validate the theory using measurements collected at Ascension Island, an equatorial station, during solar maximum conditions.