An Amateur-Radio-Based Open-Source (HW/SW) VLF/LF Receiver for Lower Ionosphere Monitoring, Examples of Identified Perturbations

Malkotsis, Filopimin; Politis, Dimitrios Z.; Dimakos, Dionisis; Potirakis, Stelios M.

doi:10.3390/foundations2030044

Cited by 3 publications

(4 citation statements)

References 52 publications

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“…The nighttime fluctuation method (NFM) was proposed for the detection of anomalies (increases or decreases) caused by ionospheric disturbances in relation with a variety of ionosphere-influencing extreme events such as EQs [Malkotsis et al, 2022;Hayakawa, 2011]. First of all, the raw nighttime amplitude data (in dB) are extracted from the diurnal variation of the amplitude data, by appropriately selecting a nighttime interval of adequate length of samples (the station records at a sampling frequency of 1 Hz), in order to exclude working (daytime) hours during which anthropogenic noise may be present.…”

Section: Nighttime Fluctuation Methods (Nfm)mentioning

confidence: 99%

“…After the calculation of the daily valued time series of the above mentioned three statistical quantities we compute their normalized values , , and as , where and are the mean value and the standard deviation of ± 15 days around the day of interest, respectively. Any statistical anomaly in these daily valued time series that exceeds could possibly be related to an EQ's preparation process or any other possibly ionosphere-influencing extreme event that can affect nighttime data [Politis et al, 2021;Hayakawa, 2011;Tatsuta et al, 2015;Malkotsis et al, 2022]. In fact, this method has recently been applied extensively to identify ionospheric anomalies prior to EQs as an increase in and decrease in and , [e.g., Rozhnoi et al, 2004;Politis et al, 2021;Hayakawa, 2011].…”

Section: Nighttime Fluctuation Methods (Nfm)mentioning

confidence: 99%

“…Various seismo-electromagnetic (seismo-EM) phenomena have been observed before earthquakes (EQs) from the ground up to space, while an enormous effort for short-term EQ prediction has already been carried out by many scientists in the last three decades [Molchanov and Hayakawa, 1995;Pulinets and Boyarchuk, 2004;Molchanov and Hayakawa, 2008;Varotsos, 2005;Hayakawa, 2019]. For example, the subionospheric monitoring of the lower ionosphere through very low to low frequency (VLF/LF) propagation has been established as a wide-spread radiotechnique for searching electromagnetic (EM) signatures in the signal (amplitude and phase) characteristics which are associated with many different extreme events such as EQs, volcanoes, geomagnetic storms, solar flares and typhoons, [e.g., Malkotsis et al, 2022;Rozhnoi et al, 2014aRozhnoi et al, , 2014bHayakawa, 2011;Nina et al, 2021].…”

Section: Introductionmentioning

confidence: 99%

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Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Politis,

Potirakis,

Contoyiannis

et al. 2023

Annals of Geophysics

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In this work we present the multi-method analysis of very low frequency (VLF) data, acquired by the radio receiver with call name UWA, located in Athens (Greece), in the University of West Attica, focusing on two strong ( ) earthquakes (EQs) that occurred in north-central mainland Greece sequentially, on 3 and 4 March 2021, with very close epicenters. Specifically, we used the data acquired from seven VLF transmitters located in Europe, North/North-West to UWA, and their propagation paths include the specific EQs epicenters. We analyzed these data using multiple analysis methods in order to investigate for possible EQ-related anomalies, taking also into account all the other possibly ionosphere-influencing extreme events that occurred during the studied period. Especially, we applied the “nighttime fluctuation method” (NFM), as well as, the “terminator time method” (TTM) in order to reveal any statistical anomaly in the nighttime amplitude recordings of VLF sub-ionospheric propagation data within 15 days before each one examined EQs. Also, we calculated the scalogram (wavelet power spectrum over time) using Morlet mother wavelet of the same nighttime data searching for possible imprints of wave-like structures during the same time period. In terms of criticality analysis, first we applied the “natural time” (NT) analysis method to the daily-valued NFM VLF propagation quantities, and subsequently applied the “method of critical fluctuations” (MCF) to the raw nighttime amplitude VLF recordings, to check for any criticality signatures up to two weeks before the examined EQs. Taking into account all the above-mentioned analysis results, we conclude that there are multiple indications that the lower ionosphere was indeed disturbed due to the preparation processes of the above-mentioned EQs, offering different types of seismogenic indications.

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Section: Nighttime Fluctuation Methods (Nfm)mentioning

confidence: 99%

Section: Nighttime Fluctuation Methods (Nfm)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Politis,

Potirakis,

Contoyiannis

et al. 2023

Annals of Geophysics

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“…Another valuable Citizen Science project is the ScintPi, a low-cost way to measure ionospheric scintillation using a GNSS receiver coupled with a RaspberryPi single-board computer (Rodrigues and Moraes, 2019). Malkotsis et al (2022) developed an amateur radio based VLF/LF receiver for lower ionospheric modeling. Serra (2023) developed amateur system for making HF elevation of arrival measurements.…”

Section: Passive Observations Of Signals Of Opportunitymentioning

confidence: 99%

Heliophysics and amateur radio: citizen science collaborations for atmospheric, ionospheric, and space physics research and operations

Frissell,

Ackermann,

Alexander

et al. 2023

Front. Astron. Space Sci.

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The amateur radio community is a global, highly engaged, and technical community with an intense interest in space weather, its underlying physics, and how it impacts radio communications. The large-scale observational capabilities of distributed instrumentation fielded by amateur radio operators and radio science enthusiasts offers a tremendous opportunity to advance the fields of heliophysics, radio science, and space weather. Well-established amateur radio networks like the RBN, WSPRNet, and PSKReporter already provide rich, ever-growing, long-term data of bottomside ionospheric observations. Up-and-coming purpose-built citizen science networks, and their associated novel instruments, offer opportunities for citizen scientists, professional researchers, and industry to field networks for specific science questions and operational needs. Here, we discuss the scientific and technical capabilities of the global amateur radio community, review methods of collaboration between the amateur radio and professional scientific community, and review recent peer-reviewed studies that have made use of amateur radio data and methods. Finally, we present recommendations submitted to the U.S. National Academy of Science Decadal Survey for Solar and Space Physics (Heliophysics) 2024–2033 for using amateur radio to further advance heliophysics and for fostering deeper collaborations between the professional science and amateur radio communities. Technical recommendations include increasing support for distributed instrumentation fielded by amateur radio operators and citizen scientists, developing novel transmissions of RF signals that can be used in citizen science experiments, developing new amateur radio modes that simultaneously allow for communications and ionospheric sounding, and formally incorporating the amateur radio community and its observational assets into the Space Weather R2O2R framework. Collaborative recommendations include allocating resources for amateur radio citizen science research projects and activities, developing amateur radio research and educational activities in collaboration with leading organizations within the amateur radio community, facilitating communication and collegiality between professional researchers and amateurs, ensuring that proposed projects are of a mutual benefit to both the professional research and amateur radio communities, and working towards diverse, equitable, and inclusive communities.

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Possible Pre-Seismic Indications Prior to Strong Earthquakes That Occurred in Southeastern Mediterranean as Observed Simultaneously by Three VLF/LF Stations Installed in Athens (Greece)

Politis

Potirakis

Sasmal³

et al. 2023

Atmosphere

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In this work, we present the analysis of VLF/LF sub-ionospheric propagation data to study anomalies possibly related to very recent strong (M > 5.5) earthquakes (EQs) that occurred in the southeastern Mediterranean in September–October 2021 and January 2022. We used the signal of one transmitter located at Negev in Israel (29.7 kHz) as received by three VLF/LF receivers (two of them using identical SW and HW) installed, at a close distance to each other, in Athens (Greece). This study employed multiple methods and techniques to analyze the reception amplitude data to identify any possible EQ-related anomalies. More specifically, first, we used both statistical and criticality analysis methods such as the “nighttime fluctuation method” (NFM), the “terminator time method” (TTM), and the “natural time” (NT) analysis method. These methods have satisfactorily been applied in the past in a series of other studies leading to interesting results. Moreover, we additionally used two more analysis techniques focusing on the signal’s amplitude characteristics. The first is the wavelet analysis of the nighttime part of the signal’s amplitude. It is based on the Morlet wavelet function, aiming to unveil the possible existence of atmospheric gravity waves (AGWs) before EQ. The second is named “long wavelength propagation capability” (LWPC), which simulates the amplitude of the signal and is based on the reflection parameters of ionosphere and by searching for increases or decreases of the electron density profile of the ionospheric D layer concerning the shifts of the minima of terminator times (TTs) in the diurnal variation of the signal. Finally, in this work, we summarize our findings and discuss possible “pre-”, “co-”, and “post-” seismic effects as observed from all the work.

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An Amateur-Radio-Based Open-Source (HW/SW) VLF/LF Receiver for Lower Ionosphere Monitoring, Examples of Identified Perturbations

Cited by 3 publications

References 52 publications

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Lower-ionosphere anomalies prior to strong earthquakes that occurred in north-central mainland Greece on March 2021 as revealed by multi-method analysis of VLF sub-ionospheric propagation data

Heliophysics and amateur radio: citizen science collaborations for atmospheric, ionospheric, and space physics research and operations

Possible Pre-Seismic Indications Prior to Strong Earthquakes That Occurred in Southeastern Mediterranean as Observed Simultaneously by Three VLF/LF Stations Installed in Athens (Greece)

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