Регистрация ионосферных возмущений с помощью приёма сигналов радиостанций РСДН-20
Authors: Корсаков А.А. , Козлов В.И. 
Published: February 2025

При мониторинге грозовой активности возникает неоднозначность интерпретации регистрируемых вариаций интенсивности естественных ОНЧ-сигналов. Неоднозначность можно исключить при одновременном приёме со схожих радиотрасс естественных и эталонных ОНЧ-радиосигналов. Приведены методика и результаты регистрации интенсивности радиошума, амплитуды и фазы радиосигналов навигационной системы РСДН-20 на частоте 11,904 кГц. Оценка межгодовых вариаций интенсивности источников радиошума в летний период с 2009 по 2017 гг. показала нарастание на 4 дБ днём и ночью. Проведена адаптация параметров регрессионной модели внезапных фазовых аномалий сигналов РСДН-20 (11,904 кГц) при регистрации в Якутске за период 2009 – 2017 гг. в зависимости от интенсивности потока рентгеновского излучения Солнца. Показано, что для описания линейной зависимости внезапных фазовых аномалий, характерной для одномодового распространения, могут использоваться вариации фазы радиосигнала на частоте 11,904 кГц при дневном распространении по радиотрассе протяжённостью 1 400 км вдоль меридиана (Хабаровск – Якутск). Зимой для радиотрасс Новосибирск – Якутск и Хабаровск – Якутск от минимума до максимума в 24-м цикле солнечной активности отмечается уменьшение чувствительности внезапных фазовых аномалий к потоку рентгеновского излучения солнечных вспышек. В летний период изменение чувствительности внезапных фазовых аномалий в 24 цикле солнечной активности не зарегистрировано.

Introduction. Geomagnetically induced currents due to disturbances in the magnetosphere and ionosphere can disrupt the operation of power lines, railway automation systems, and pipelines. Geomagnetic disturbances in the magnetosphere and ionosphere can disrupt the operation of power lines, railway automation systems, and pipelines. Understanding how the ionosphere reacts to solar radiation and atmospheric changes is still important. Changes in the amplitude and phase of VLF radio signals can tell us a lot about variations in the lower ionosphere. However, when we record these variations at different frequencies, it's not always clear if they're due to changes in the signal source or changes in the Earth-ionosphere waveguide parameters. To remove this ambiguity, we receive both natural and reference VLF radio signals from similar transmission paths. Additionally, over short radio paths, higher order modes can significantly contribute to the overall signal due to their interference. The objectives of this study are twofold. First, we aimed to analyze the interannual variations in the intensity of VLF radio noise sources during the summer season. Second, we intend to examine the parameters of a linear regression model for sudden phase anomalies in radio signals at 11.904 kHz. These anomalies are dependent on X-ray flux levels during solar flares at different stages of the 24th solar cycle (increasing, maximum, and decreasing). To achieve these goals, we were need to choose a method for recording the intensity of radio noise, as well as the amplitude and phase of VLF signals from transmitters in similar directions. Furthermore, we investigated interannual variations in the intensity of VLF radio noise sources during summer, focusing on variations in radio noise intensity and the amplitude of radio transmitter signals recorded at 11.904 kHz under normal conditions of the lower ionosphere. Lastly, we adjusted the parameters of a linear regression model for sudden phase anomalies (SPAs) based on variations in the solar X-ray flux's intensity and phase fluctuations in VLF radio signals recorded between 2009 and 2017 at 11.904 kHz on radio paths across Northern Eurasia. Research methods. We measured the intensity of radio noise, as well as the amplitude and phase of RSDN-20 radio signals recorded in Yakutsk. Results. The intensity of radio noise sources at 11.904 kHz increased by 4 dB during both daytime and nighttime from 2009 to 2017. The parameters of the SPA model for RSDN-20 signals at 11.904 kHz were adapted. Conclusions. The period of recording VLF radio noise intensity, as well as the amplitude and phase of radio signals from 2009 to 2017, covered the entire span of the 24th solar cycle, including its rise, peak, and decline. The increase in thunderstorm activity during this period may be attributed to the warming trends observed. The variations in radio signal phase at 11.904 kHz during daytime propagation over a 1400 km-long meridional radio path (Khabarovsk-to-Yakutsk) can be used to describe the linear relationship between SPA and solar flares' X-ray flux. For the propagation paths Novosibirsk-to-Yakutsk and Khabarovsk-to-Yakutsk in winter, from the minimum to the maximum of the 24th solar cycle, the SPA sensitivity to X-ray flux from solar flares decreased. The scientific importance of these results lies in the development of a method for recording VLF radio noise intensity, amplitude, and phase of RSDN-20 radio signals. In practical terms, the experimental data can be applied to estimate variations in the parameters of the Earth-ionosphere waveguide when designing new systems. Additionally, the SPA model can find utility in the development of ground-based methods for assessing X-ray flux intensity during solar activity.