Polarization of Narrowband VLF Transmitter Signals as an Ionospheric Diagnostic
Polarization of Narrowband VLF Transmitter Signals as an Ionospheric Diagnostic
复制标题
DOI：
10.1002/2017ja024907
复制
发表时间：
2018-01-01
影响因子：
2.8
通讯作者：
Golkowski, M.
中科院分区：
文献类型：
--
作者：
Gross, N. C.;Cohen, M. B.;Golkowski, M.
甚低频（VLF，3-30 kHz）发射机遥感长期以来一直被用作D区电离层（60-90 km）的一种简单而有用的诊断方法。它所需要的只是一个VLF无线电接收器，用于记录信标信号的幅度和/或相位作为时间的函数。在环境和干扰条件下，接收到的信号可以与理论模型的预测进行比较，以推断电离层波导特性，如电子密度。在大多数情况下，振幅和相位都作为单独的数据流进行分析，通常只使用振幅。散射场公式有效地组合了幅度和相位，但没有解决如何联合收割机组合两个磁场分量。我们提出了使用两个水平分量的磁场的甚低频发射机信号的极化椭圆分析。极化椭圆的形状不随源相位的变化而变化，这避免了VLF发射机具有未知源相位的重要问题。介绍了一种同步双通道MSK解调算法，以消除水平磁场分量之间相位差的90度模糊。此外，同步解调改善了低SNR条件下的相位测量。使用极化椭圆制剂，我们需要一个新的眼光在昼夜甚低频发射机的变化，环境条件，和电离层干扰太阳耀斑，闪电电离层加热，闪电引起的电子降水，并找到不同的签名在极化椭圆。
Very low frequency (VLF, 3-30 kHz) transmitter remote sensing has long been used as a simple yet useful diagnostic for the D region ionosphere (60-90 km). All it requires is a VLF radio receiver that records the amplitude and/or phase of a beacon signal as a function of time. During both ambient and disturbed conditions, the received signal can be compared to predictions from a theoretical model to infer ionospheric waveguide properties like electron density. Amplitude and phase have in most cases been analyzed each as individual data streams, often only the amplitude is used. Scattered field formulation combines amplitude and phase effectively, but does not address how to combine two magnetic field components. We present polarization ellipse analysis of VLF transmitter signals using two horizontal components of the magnetic field. The shape of the polarization ellipse is unchanged as the source phase varies, which circumvents a significant problem where VLF transmitters have an unknown source phase. A synchronized two-channel MSK demodulation algorithm is introduced to mitigate 90 degrees ambiguity in the phase difference between the horizontal magnetic field components. Additionally, the synchronized demodulation improves phase measurements during low-SNR conditions. Using the polarization ellipse formulation, we take a new look at diurnal VLF transmitter variations, ambient conditions, and ionospheric disturbances from solar flares, lightning-ionospheric heating, and lightning-induced electron precipitation, and find differing signatures in the polarization ellipse.