Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities
Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities
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DOI：
10.1051/swsc/2023021
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发表时间：
2023-11-07
影响因子：
3.3
通讯作者：
Blaszkiewicz，Leszek
中科院分区：
文献类型：
--
作者：
Flisek，Pawel;Forte，Biagio;Blaszkiewicz，Leszek
电离层等离子体密度内的不均匀性会影响跨电离层无线电信号，导致信号幅度和相位的无线电波闪烁。由电离层不规则性引起的闪烁量通常随无线电波频率而减小。由于电离层影响各种技术系统（例如，由于电离层的影响（包括民用航空、金融业务）以及低频射电天文学观测，必须以比目前更高的准确度探测和监测电离层的影响。在这里，一种新的方法，电离层的不规则性的检测和表征的基础上建立的LOFAR（低频阵列）闪烁测量在甚高频（VHF），考虑到缺乏遍历性的强度波动引起的闪烁。该方法估计theS 4闪烁指数起源于不规则性与空间尺度的惯性子范围内的电子密度波动在电离层。该方法通过设在Baidndy、Borowiec和Eupazy的波兰LOFAR台站收集的观测数据加以说明：通过将LOFAR甚高频闪烁观测数据与通过设在Baidndy LOFAR台站附近的高速率接收器以及通过波兰ASG-EUPOS网络的大地测量接收器收集的独立全球导航卫星系统观测数据进行比较，对该方法进行了验证。两个案例研究：2017年3月31日和2017年9月28日。LOFAR 4观测结果与全球导航卫星系统对电离层闪烁和总电子含量变化率的独立测量结果之间的比较表明，由于无线电波闪烁的频率依赖性，LOFAR和全球导航卫星系统对电离层结构的敏感性是不同的。此外，还可以注意到，LOFAR甚高频闪烁观测可用于探测中纬度电离层形成的等离子体结构，包括通过传统的全球导航卫星系统测量不一定探测到的空间尺度上的电子密度梯度：探测所有空间尺度对于正确监测电离层过程和建立电离层过程模型十分重要。因此，除了传统的全球导航卫星系统电离层测量之外，LOFAR对电离层结构的不同敏感度使我们能够扩大对电离层过程的了解。
Inhomogeneities within the ionospheric plasma density affect trans-ionospheric radio signals, causing radio wave scintillation in the amplitude and phase of the signals. The amount of scintillation induced by ionospheric irregularities typically decreases with the radio wave frequency. As the ionosphere affects a variety of technological systems (e.g., civil aviation, financial operations) as well as low-frequency radio astronomy observations, it is important to detect and monitor ionospheric effects with higher accuracy than currently available. Here, a novel methodology for the detection and characterization of ionospheric irregularities is established on the basis of LOFAR (Low-Frequency Array) scintillation measurements at Very High Frequency (VHF) that take into account the lack of ergodicity in the intensity fluctuations induced by scintillation. The methodology estimates theS4scintillation index originating from irregularities with spatial scales in the inertial sub-range of electron density fluctuations in the ionosphere. The methodology is illustrated by means of observations that were collected through the Polish LOFAR stations located in Bałdy, Borowiec and Łazy: its validation was carried out by comparing LOFAR VHF scintillation observations with independent Global Navigation Satellite Systems (GNSS) observations that were collected through a high-rate receiver located near the LOFAR station in Bałdy as well as through geodetic receivers from the Polish ASG-EUPOS network. Two case studies are presented: 31 March 2017 and 28 September 2017. The comparison between LOFARS4observations and independent ionospheric measurements of both scintillation and rate of change of Total Electron Content (TEC) from GNSS reveals that the sensitivity of LOFAR and GNSS to ionospheric structures is different as a consequence of the frequency dependency of radio wave scintillation. Furthermore, it can be noticed that observations of LOFAR VHF scintillation can be utilised to detect plasma structures forming in the mid-latitude ionosphere, including electron density gradients occurring over spatial scales that are not necessarily detected through traditional GNSS measurements: the detection of all spatial scales is important for correct monitoring and modelling of ionospheric processes. Hence, the different sensitivity of LOFAR to ionospheric structures, in addition to traditional GNSS ionospheric measurements, allows us to expand the knowledge of ionospheric processes.