P. Ponomarenko;M. Ghalamkarian Nejad;A. V. Koustov
It has been previously established that the Doppler velocities of F-region ionospheric echoes observed by the Super Dual Auroral Radar Network (SuperDARN) at high frequencies (HF, 8–20 MHz) are persistently lower than those measured by other instruments at the same locations. This was attributed to the ionospheric refractive index for HF radio waves being noticeably smaller than one. The refractive index values can be obtained in two ways: based on electron density estimates from a co-located instrument or a model, or by deriving them from SuperDARN elevation angle data. To compare these methods, we considered line-of-sight Doppler velocity observations by the Rankin Inlet (RKN) SuperDARN radar and the Resolute Bay Incoherent Scatter Radars (RISR). The velocity data were supplemented by electron density measurements from RISR. The elevation angle data were also used for accurate determination of SuperDARN echo geolocation because the actual ground range to the echo location may significantly differ from that obtained with the conventional SuperDARN models. The RISR Doppler velocity values were used as a reference to the RKN observations via 0.5-hop and 1.5-hop propagation paths. Correction by the index of refraction based on both maximum electron density from the RISR and elevation angle data from RKN brought 0.5-hop data close to the RISR velocity values, with the latter representing a self-contained approach. However, for 1.5-hop echoes from the polar cap, the uncorrected SuperDARN velocities exceeded those from RISR. We discuss potential causes of this apparent anomaly.
{"title":"Application of SuperDARN interferometry for improved estimates of Doppler velocity and echo geolocation","authors":"P. Ponomarenko;M. Ghalamkarian Nejad;A. V. Koustov","doi":"10.1029/2024RS008084","DOIUrl":"https://doi.org/10.1029/2024RS008084","url":null,"abstract":"It has been previously established that the Doppler velocities of F-region ionospheric echoes observed by the Super Dual Auroral Radar Network (SuperDARN) at high frequencies (HF, 8–20 MHz) are persistently lower than those measured by other instruments at the same locations. This was attributed to the ionospheric refractive index for HF radio waves being noticeably smaller than one. The refractive index values can be obtained in two ways: based on electron density estimates from a co-located instrument or a model, or by deriving them from SuperDARN elevation angle data. To compare these methods, we considered line-of-sight Doppler velocity observations by the Rankin Inlet (RKN) SuperDARN radar and the Resolute Bay Incoherent Scatter Radars (RISR). The velocity data were supplemented by electron density measurements from RISR. The elevation angle data were also used for accurate determination of SuperDARN echo geolocation because the actual ground range to the echo location may significantly differ from that obtained with the conventional SuperDARN models. The RISR Doppler velocity values were used as a reference to the RKN observations via 0.5-hop and 1.5-hop propagation paths. Correction by the index of refraction based on both maximum electron density from the RISR and elevation angle data from RKN brought 0.5-hop data close to the RISR velocity values, with the latter representing a self-contained approach. However, for 1.5-hop echoes from the polar cap, the uncorrected SuperDARN velocities exceeded those from RISR. We discuss potential causes of this apparent anomaly.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-15"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. A. D. Fiori;A. Kero;R. Gillies;T. G. Cameron;C. Cully;R. Ghaffari
High frequency radio wave propagation is sensitive to absorption in the D and lower E-region ionosphere. Absorption models typically characterize attenuation expected at 30 MHz, meaning scaling relationships are required to map to absorption expected at other frequencies. This is important when evaluating absorption at <20 MHz, as these frequencies are typically used for communication, and are highly sensitive to ionospheric disturbances. Typically, a power law relationship between absorption and frequency with a coefficient of n = − 2 is used. This relationship can be demonstrated through consideration of the Appleton-Hartree equation. This paper examines the performance of this relationship using data from the Kilpisjärvi Atmospheric Imaging Receiver Array for 13–14 November 2012. Using absorption measured at 30 MHz as a baseline, the power law relationship was used to calculated absorption at frequencies of 10–80 MHz. For this event, the power law relationship performed well when the measured absorption at 30 MHz was <1–2 dB, but strongly overestimated measurements as absorption increased. Performance improved when n was allowed to vary as a function of the overall level of absorption at 30 MHz. This accounts for local ionospheric changes associated with absorption events that change the balance of parameters in the Appleton-Hartree equation causing deviation from n = − 2. To further accommodate deviations associated with both local ionospheric disturbances and ambient electromagnetic noise contributions, an empirical relationship relating the logarithm of absorption to frequency was evaluated as a function of overall absorption. Compared to the simplified n = − 2 power law relationship between absorption and frequency, the new relationship better represents measured absorption for the event studied.
{"title":"Examining the power law relationship between absorption and frequency using spectral riometer data","authors":"R. A. D. Fiori;A. Kero;R. Gillies;T. G. Cameron;C. Cully;R. Ghaffari","doi":"10.1029/2024RS007951","DOIUrl":"https://doi.org/10.1029/2024RS007951","url":null,"abstract":"High frequency radio wave propagation is sensitive to absorption in the D and lower E-region ionosphere. Absorption models typically characterize attenuation expected at 30 MHz, meaning scaling relationships are required to map to absorption expected at other frequencies. This is important when evaluating absorption at <20 MHz, as these frequencies are typically used for communication, and are highly sensitive to ionospheric disturbances. Typically, a power law relationship between absorption and frequency with a coefficient of n = − 2 is used. This relationship can be demonstrated through consideration of the Appleton-Hartree equation. This paper examines the performance of this relationship using data from the Kilpisjärvi Atmospheric Imaging Receiver Array for 13–14 November 2012. Using absorption measured at 30 MHz as a baseline, the power law relationship was used to calculated absorption at frequencies of 10–80 MHz. For this event, the power law relationship performed well when the measured absorption at 30 MHz was <1–2 dB, but strongly overestimated measurements as absorption increased. Performance improved when n was allowed to vary as a function of the overall level of absorption at 30 MHz. This accounts for local ionospheric changes associated with absorption events that change the balance of parameters in the Appleton-Hartree equation causing deviation from n = − 2. To further accommodate deviations associated with both local ionospheric disturbances and ambient electromagnetic noise contributions, an empirical relationship relating the logarithm of absorption to frequency was evaluated as a function of overall absorption. Compared to the simplified n = − 2 power law relationship between absorption and frequency, the new relationship better represents measured absorption for the event studied.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-14"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article introduces the concept, theory, and design of an angle and polarization insensitive radar cross section (RCS) reduction metasurface, using a hybrid mechanism of polarization conversion and absorption. By introducing ladder- and rectangle-shaped metallic patches in the vertical dimension of a 3-D structure, polarization conversion rate (PCR) deterioration, brought by the increase of equivalent substrate thickness at oblique incidences, can be suppressed. Furthermore, lumped resistors are loaded at proper places in each polarization conversion cell, to achieve the power absorption while maintain the angular insensitivity of the PCR. With the above hybrid mechanism, a stable 10-dB RCS reduction can be achieved regardless of the angle of incidence in a wide range and polarization directions. An equivalent circuit model is established for explaining the physical mechanism of the proposed metasurface. For validation, a prototype is fabricated and tested. Measurement results indicate that, for both monostatic RCS at the normal incidence and specular RCS of off-normal incidences from 0° to 45°, a 10-dB TE- and TM-mode RCS reduction can be achieved in the entire X-band (8–12 GHz) and Ku-band (12–18 GHz).
{"title":"Angle and polarization insensitive RCS reduction metasurface based on hybrid mechanism of polarization conversion and absorption","authors":"H. J. Zhao;X. Y. Dai;H. Chu;X. H. Zhu;Y. X. Guo","doi":"10.1029/2024RS008052","DOIUrl":"https://doi.org/10.1029/2024RS008052","url":null,"abstract":"This article introduces the concept, theory, and design of an angle and polarization insensitive radar cross section (RCS) reduction metasurface, using a hybrid mechanism of polarization conversion and absorption. By introducing ladder- and rectangle-shaped metallic patches in the vertical dimension of a 3-D structure, polarization conversion rate (PCR) deterioration, brought by the increase of equivalent substrate thickness at oblique incidences, can be suppressed. Furthermore, lumped resistors are loaded at proper places in each polarization conversion cell, to achieve the power absorption while maintain the angular insensitivity of the PCR. With the above hybrid mechanism, a stable 10-dB RCS reduction can be achieved regardless of the angle of incidence in a wide range and polarization directions. An equivalent circuit model is established for explaining the physical mechanism of the proposed metasurface. For validation, a prototype is fabricated and tested. Measurement results indicate that, for both monostatic RCS at the normal incidence and specular RCS of off-normal incidences from 0° to 45°, a 10-dB TE- and TM-mode RCS reduction can be achieved in the entire X-band (8–12 GHz) and Ku-band (12–18 GHz).","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-11"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study introduces the development of a flexible and compact radiator using a jeans material as a substrate for wireless body area network (WBAN) applications. A fabric made of jeans with a thickness of 0.6 mm, a tangent loss (tan δ) of 0.02, and a dielectric constant (εr) of 1.6 is used for designing an element with dimensions of 18.5 × 27 × 0.6 mm3. The jeans substrate incorporates a triangular feed structure on top and a defected ground structure on its back. This design enables a span ranging from 3.41 to more than 20 GHz, with a magnitude of S11 < —10 dB, a peak gain of 4.48 dBi, and a peak efficiency of 97.28%. The system is designed for Ultra-wideband (UWB) integrated with Ku band. The measurement findings are very consistent with the results obtained from the models. The suggested antenna is highly appropriate for WBAN applications because of its thin profile, flexible design, and compatibility with WBAN and UWB technologies.
{"title":"A novel flexible ultra wide band wearable slot antenna with defected ground for WBAN applications","authors":"Nageswara Rao Regulagadda;U. V. Ratna Kumari","doi":"10.1029/2024RS008085","DOIUrl":"https://doi.org/10.1029/2024RS008085","url":null,"abstract":"This study introduces the development of a flexible and compact radiator using a jeans material as a substrate for wireless body area network (WBAN) applications. A fabric made of jeans with a thickness of 0.6 mm, a tangent loss (tan δ) of 0.02, and a dielectric constant (εr) of 1.6 is used for designing an element with dimensions of 18.5 × 27 × 0.6 mm<sup>3</sup>. The jeans substrate incorporates a triangular feed structure on top and a defected ground structure on its back. This design enables a span ranging from 3.41 to more than 20 GHz, with a magnitude of S11 < —10 dB, a peak gain of 4.48 dBi, and a peak efficiency of 97.28%. The system is designed for Ultra-wideband (UWB) integrated with Ku band. The measurement findings are very consistent with the results obtained from the models. The suggested antenna is highly appropriate for WBAN applications because of its thin profile, flexible design, and compatibility with WBAN and UWB technologies.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-14"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Digital Radio Mondiale (DRM) is a digital Orthogonal Frequency Division Multiplexing (OFDM) broadcasting standard that has been employed all over the world. The operating carrier frequency and time of DRM station change with the scheduling period. The user terminal commonly uses channel decoding and audio decoding to detect the DRM radio. This conventional signal detection method always fail when the station is not working, or the signal-to-noise ratio (SNR) is weak, or the designated frequency band is illegally occupied. Besides, the conventional method needs at least one DRM transmission super frame with a duration of 1.2 s, which causes delay and brings additional computations. To solve the challenges faced by conventional method, this paper has proposed an agile and efficient signal detection method based on the Generalized Likelihood Ratio Test. The proposed method coherently integrates the frequency pilots of successive OFDM symbols via discrete Fourier transform, then propose a sufficient statistic to detect the DRM radio. The required number of OFDM symbols, which is much smaller than that of one transmission super frame, is adaptively chosen from the given probabilities of false alarm and correct detection. The computations and SNR requirement of the proposed method are both smaller than the conventional method, which help the user terminal quickly detect the DRM signal over the given frequency band. The proposed method also provides a new perspective for electromagnetic spectrum management.
{"title":"Agile detection of DRM signal via GLRT","authors":"Yangpeng Dan;Luyao Wang;Chaofan Duan;Fan Yang","doi":"10.1029/2024RS008164","DOIUrl":"https://doi.org/10.1029/2024RS008164","url":null,"abstract":"Digital Radio Mondiale (DRM) is a digital Orthogonal Frequency Division Multiplexing (OFDM) broadcasting standard that has been employed all over the world. The operating carrier frequency and time of DRM station change with the scheduling period. The user terminal commonly uses channel decoding and audio decoding to detect the DRM radio. This conventional signal detection method always fail when the station is not working, or the signal-to-noise ratio (SNR) is weak, or the designated frequency band is illegally occupied. Besides, the conventional method needs at least one DRM transmission super frame with a duration of 1.2 s, which causes delay and brings additional computations. To solve the challenges faced by conventional method, this paper has proposed an agile and efficient signal detection method based on the Generalized Likelihood Ratio Test. The proposed method coherently integrates the frequency pilots of successive OFDM symbols via discrete Fourier transform, then propose a sufficient statistic to detect the DRM radio. The required number of OFDM symbols, which is much smaller than that of one transmission super frame, is adaptively chosen from the given probabilities of false alarm and correct detection. The computations and SNR requirement of the proposed method are both smaller than the conventional method, which help the user terminal quickly detect the DRM signal over the given frequency band. The proposed method also provides a new perspective for electromagnetic spectrum management.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-15"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junda Jin;Jie Liu;Dong Liu;Jiang-Qiao Ding;Xuan Zhang;Jing Li;Sheng-Cai Shi
The noise of a cryogenic low-noise amplifier (cryo-LNA) directly impacts the sensitivity of a terahertz superconducting heterodyne receiver. This paper aims to evaluate the noise temperature of a cryo-LNA and its suitability as the first stage IF amplifier for the heterodyne receiver, specifically the high-sensitivity terahertz detection module for the China Space Station Survey Telescope. Both the Cold Attenuator (CA) Method and the Variable Temperature Load (VTL) Method are employed to ensure confidence in the measured values. The maximum difference in results is 1K within the frequency range of 0.1–2 GHz, contributing to an uncertainty of 4K in the receiver's noise temperature. The measurement accuracy of the noise temperature is analyzed in detail, with particular emphasis on the influence of the cryogenic attenuator and the noise contribution from the connecting cable with a temperature gradient. Additionally, the dependence of the cryo-LNA's noise temperature on physical temperature and radiation hardness are verified to assess suitability for space applications.
{"title":"The noise temperature analysis on a space-grade cryogenic low noise amplifier using two measurement methods","authors":"Junda Jin;Jie Liu;Dong Liu;Jiang-Qiao Ding;Xuan Zhang;Jing Li;Sheng-Cai Shi","doi":"10.1029/2024RS008023","DOIUrl":"https://doi.org/10.1029/2024RS008023","url":null,"abstract":"The noise of a cryogenic low-noise amplifier (cryo-LNA) directly impacts the sensitivity of a terahertz superconducting heterodyne receiver. This paper aims to evaluate the noise temperature of a cryo-LNA and its suitability as the first stage IF amplifier for the heterodyne receiver, specifically the high-sensitivity terahertz detection module for the China Space Station Survey Telescope. Both the Cold Attenuator (CA) Method and the Variable Temperature Load (VTL) Method are employed to ensure confidence in the measured values. The maximum difference in results is 1K within the frequency range of 0.1–2 GHz, contributing to an uncertainty of 4K in the receiver's noise temperature. The measurement accuracy of the noise temperature is analyzed in detail, with particular emphasis on the influence of the cryogenic attenuator and the noise contribution from the connecting cable with a temperature gradient. Additionally, the dependence of the cryo-LNA's noise temperature on physical temperature and radiation hardness are verified to assess suitability for space applications.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-10"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper introduces an innovative blind adaptive 3D Beam steering algorithm designed to mitigate interference, ultimately improving the signal-to-interference and noise ratio (SINR) to enhance the overall performance of mMIMO (massive multiple-input multiple-output (MIMO)) networks. The proposed algorithm combines an optimized direction of arrival (DoA) estimation method with an inventive adaptive signal processing technique. To address the computational complexity associated with determining the 2D-DoA of incoming signals, an improved RD-MUSIC (Reduced Dimension — Multiple Signal Classification) estimator is proposed. This method streamlines the process into an efficient 1D search, significantly reducing computational overhead compared to conventional 2D-MUSIC and minimizing noise, maintaining superior accuracy over the conventional RD-MUSIC method. Leveraging the estimated 2D-DoAs, the proposed adaptive signal processing technique integrates the Dolph-Chebyshev weighting method with nulling constraints to calculate the optimal complex weig0hts necessary to accurately steer the main Beam toward the desired signal direction and create deep nulls in the directions of interfering signals, resulting in enhanced SINR. Compared to alternative algorithms, our approach demonstrates superior performance and offers an efficient solution without requiring a training signal or additional antenna elements. This is advantageous, particularly in environments with intense interference and high mobility, making it a promising candidate for future wireless systems.
{"title":"A novel blind adaptive 3D beam steering algorithm for interference mitigation and performance enhancement in massive MIMO systems","authors":"Hosni Manai;Larbi Ben Hadj Slama;Ridha Bouallegue","doi":"10.1029/2024RS008075","DOIUrl":"https://doi.org/10.1029/2024RS008075","url":null,"abstract":"This paper introduces an innovative blind adaptive 3D Beam steering algorithm designed to mitigate interference, ultimately improving the signal-to-interference and noise ratio (SINR) to enhance the overall performance of mMIMO (massive multiple-input multiple-output (MIMO)) networks. The proposed algorithm combines an optimized direction of arrival (DoA) estimation method with an inventive adaptive signal processing technique. To address the computational complexity associated with determining the 2D-DoA of incoming signals, an improved RD-MUSIC (Reduced Dimension — Multiple Signal Classification) estimator is proposed. This method streamlines the process into an efficient 1D search, significantly reducing computational overhead compared to conventional 2D-MUSIC and minimizing noise, maintaining superior accuracy over the conventional RD-MUSIC method. Leveraging the estimated 2D-DoAs, the proposed adaptive signal processing technique integrates the Dolph-Chebyshev weighting method with nulling constraints to calculate the optimal complex weig0hts necessary to accurately steer the main Beam toward the desired signal direction and create deep nulls in the directions of interfering signals, resulting in enhanced SINR. Compared to alternative algorithms, our approach demonstrates superior performance and offers an efficient solution without requiring a training signal or additional antenna elements. This is advantageous, particularly in environments with intense interference and high mobility, making it a promising candidate for future wireless systems.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"60 1","pages":"1-23"},"PeriodicalIF":1.6,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper mainly examines the response of variation of the TEC, foF2, and hmF2 obtained from observations (GPS and digisondes) and models (IRI 2016 and IRI-Plas 2017) across low-to-high latitudes during various geomagnetic storm time conditions in different solar activity years. The 19 February 2014, 17 March 2015, and 4 November 2021 geomagnetic storm cases caused positive storm effects (particularly at low latitudes), while the 8 September 2017, and 26 August 2018 geomagnetic storm cases resulted in negative storm effects, especially at mid and high latitudes. Furthermore, during the 19 February 2014 storm, the sharp increase (peak) diurnal digisondes TEC values are observed, on average, when the hmF2 values reach about 360, 282, and 312 km, in the low, mid and high latitudes, respectively. During the 26 August 2018 storm, the peak TEC values are observed, on average, when the hmF2 values reach about 313, 258, and 268 km in the low, mid and high latitudes, respectively. Hence, the digisonde-derived peak TEC in mid latitudes typically coincides with a decrease in hmF2, while in low latitudes, it is associated with an increase in hmF2. Additionally, during low solar activity periods, digisonde-derived peak TEC values were observed when hmF2 decreased, contrasting with patterns seen during high solar activity. Both the IRI 2016 and IRI-Plas 2017 models performed well, with the models peak TEC values being observed when the hmF2 variations attain similar values with the observations, reinforcing the models' reliability in capturing ionospheric responses during geomagnetic storms.
{"title":"The geomagnetic storm time responses of the TEC, foF2, and hmF2 in different solar activity during solar cycle 24 and 25","authors":"Yekoye Asmare Tariku","doi":"10.1029/2024RS007961","DOIUrl":"https://doi.org/10.1029/2024RS007961","url":null,"abstract":"This paper mainly examines the response of variation of the TEC, foF2, and hmF2 obtained from observations (GPS and digisondes) and models (IRI 2016 and IRI-Plas 2017) across low-to-high latitudes during various geomagnetic storm time conditions in different solar activity years. The 19 February 2014, 17 March 2015, and 4 November 2021 geomagnetic storm cases caused positive storm effects (particularly at low latitudes), while the 8 September 2017, and 26 August 2018 geomagnetic storm cases resulted in negative storm effects, especially at mid and high latitudes. Furthermore, during the 19 February 2014 storm, the sharp increase (peak) diurnal digisondes TEC values are observed, on average, when the hmF2 values reach about 360, 282, and 312 km, in the low, mid and high latitudes, respectively. During the 26 August 2018 storm, the peak TEC values are observed, on average, when the hmF2 values reach about 313, 258, and 268 km in the low, mid and high latitudes, respectively. Hence, the digisonde-derived peak TEC in mid latitudes typically coincides with a decrease in hmF2, while in low latitudes, it is associated with an increase in hmF2. Additionally, during low solar activity periods, digisonde-derived peak TEC values were observed when hmF2 decreased, contrasting with patterns seen during high solar activity. Both the IRI 2016 and IRI-Plas 2017 models performed well, with the models peak TEC values being observed when the hmF2 variations attain similar values with the observations, reinforcing the models' reliability in capturing ionospheric responses during geomagnetic storms.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 12","pages":"1-18"},"PeriodicalIF":1.6,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The utilization of the global navigation satellite systems (GNSS) services in both military and civilian applications as well as for scientific investigation has grown exponentially. However, the increasing reliance on GNSS applications has raised concerns about potential risks from intentional radio frequency interference (RFI) transmitters. RFI significantly affects GNSS's environmental monitoring capabilities by inflating the scintillation index and misleading the scientific community with scintillation indices not attributable to ionospheric dynamic events. Consequently, the existing climatological distribution of GNSS scintillations may require careful reevaluation, as it may not adequately filter out RFI induced scintillations. Thus, characterizing the global RFI occurrence regions and developing real-time detection capabilities to mitigate its effects is critically important. Leveraging GNSS measurements from ground stations and six COSMIC-2 satellite constellations, we have developed a technique to detect RFI events and identify RFI active regions. Additionally, for the first time, we have implemented techniques that differentiate RFI associated scintillations from scintillations caused by ionospheric turbulence.
{"title":"The impact and sources of radio frequency interference on GNSS signals","authors":"Endawoke Yizengaw","doi":"10.1029/2024RS008109","DOIUrl":"https://doi.org/10.1029/2024RS008109","url":null,"abstract":"The utilization of the global navigation satellite systems (GNSS) services in both military and civilian applications as well as for scientific investigation has grown exponentially. However, the increasing reliance on GNSS applications has raised concerns about potential risks from intentional radio frequency interference (RFI) transmitters. RFI significantly affects GNSS's environmental monitoring capabilities by inflating the scintillation index and misleading the scientific community with scintillation indices not attributable to ionospheric dynamic events. Consequently, the existing climatological distribution of GNSS scintillations may require careful reevaluation, as it may not adequately filter out RFI induced scintillations. Thus, characterizing the global RFI occurrence regions and developing real-time detection capabilities to mitigate its effects is critically important. Leveraging GNSS measurements from ground stations and six COSMIC-2 satellite constellations, we have developed a technique to detect RFI events and identify RFI active regions. Additionally, for the first time, we have implemented techniques that differentiate RFI associated scintillations from scintillations caused by ionospheric turbulence.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 12","pages":"1-12"},"PeriodicalIF":1.6,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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