Radio Science最新文献

{"title":"Multi-scale characterization of ionospheric disturbances over east africa during 17 March 2015 St. Patrick's day geomagnetic storm","authors":"Edward Uluma;Atirsaw Muluye Tilahun;Solomon Otoo Lomotey;Moses Mefe;Wilberforce Muniafu;Joseph Kagotho Muriithi;Awuor Adero;Daniel Okoh;Boniface Ndinya","doi":"10.1029/2025RS008497","DOIUrl":"https://doi.org/10.1029/2025RS008497","url":null,"abstract":"We investigate the ionospheric response to the intense St. Patrick's Day geomagnetic storm of 17 March 2015 (minimum Dst ≈ —223 nT) using Global Navigation Satellite System (GNSS)-derived Total Electron Content (TEC) observations from 11 East African stations: Addis Ababa-ADIS (9.04°N, 38.77°E), Arusha-ARSH (3.38°S, 36.69°E), Dodoma-DODM (6.19°S, 35.75°E), Eldoret-MOIU (0.29°N, 35.29°E), Malindi-MAL2 (2.99°S, 40.19°E), Mbarara-MBAR (0.61°S, 30.65°E), and Mbeya-MBEY (9.03°N, 38.74°E, Asab-ASAB (13.06°N. 43.65°E), Ginr-GINR (7.15°N, 40.71°E), Bahir Dar-BDMT (11.60°N, 37.36°E), Debarek-DEBK (13.15°N, 37.89°E), Assosa-ASOS (10.05°N, 34.55°E). Instrumental biases were removed, data were screened for satellite elevation angles ≥40°, and analyzed using detrended TEC (dTEC) and Morlet continuous wavelet transform to identify storm-time ionospheric disturbances across multiple temporal scales. The storm main phase was characterized by prolonged southward z-component of interplanetary magnetic field (IMF-Bz) (<—20>600 kms⁻¹), and elevated y-component of the interplanetary electric field (IEF-Ey), indicating strong solar wind-magnetosphere coupling. These conditions drove significant ionospheric variability, with the largest dTEC amplitudes (>±4 TECU) observed near the Equatorial Ionization Anomaly (EIA), particularly at ADIS and MAL2. Wavelet analysis revealed the coexistence of medium-scale traveling ionospheric disturbances (MSTIDs; ∼0.25-1 hr), large-scale travelling ionospheric disturbances (LSTIDs; ∼1–4 hr), and short-period fluctuations (<0.25 hr). Disturbances were most pronounced during the storm main and early recovery phases and exhibited clear latitudinal dependence, with enhanced activity near the EIA crest. Post-sunset ionospheric irregularities, interpreted as equatorial plasma bubbles (EPBs), were identified through sharp dTEC depletions and enhanced short-period wavelet power. EPBs occurred on most days but showed increased frequency, earlier onset, and wider latitudinal extent during the storm, consistent with intensified pre-reversal enhancement and storm-time electric field penetration. The temporal association between MSTIDs and EPB onset suggests a potential seeding role of atmospheric wave activity. These results demonstrate that ionospheric disturbances over East Africa are strongly controlled by the interplay between storm-time electrodynamics and equatorial processes. The study highlights the effectiveness of combined dTEC and wavelet analysis for resolving multiscale ionospheric variability and provides important insights into space weather impacts on GNSS performance in equatorial regions.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-27"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148902860","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}

{"title":"Relationship between riometer absorption and mediumand high-frequency auroral absorption: Vertical incidence","authors":"A. J. Foppiano;M. A. Bravo","doi":"10.1029/2025RS008587","DOIUrl":"https://doi.org/10.1029/2025RS008587","url":null,"abstract":"Some known factors influencing the accuracy of D- and E-region ionospheric radio absorption estimates at auroral latitudes, determined from Riometer (Relative Ionospheric Opacity Meter) measurements of incident cosmic noise, are briefly reviewed. Then, measured and modeled height distributions of electron concentration at auroral latitudes, corresponding to various levels of auroral radio-wave absorption determined by riometers, are analyzed. It is first confirmed that riometer absorption can be equated to vertical incidence absorption on the upward or downward legs. Then the frequency dependence of absorption is derived for the Medium Frequency (MF) and High Frequency (HF) ranges at vertical incidence. In both cases, absorption values at different frequencies are calculated using the phase-integral method, incorporating realistic height distributions of effective electron-neutral particle collision frequencies. The results indicate that the frequency dependence deviates from that observed at low and middle latitudes, particularly when absorption levels are high. It is proposed that the found changes to the frequency dependence for auroral latitudes may be used for practical estimations of absorption on MF and HF propagation predictions at vertical incidence, based on the widely available riometer observations. In a companion paper, formulae are proposed to determine oblique-incidence absorption in MF-HF propagation predictions using vertical-incidence estimates.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-17"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148902984","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}

{"title":"A novel combined dual network for mmWave hand gesture recognition","authors":"Xiangqun Zhang;Zhizhou Ge;Meiqi Zhou;Genyuan Du;Guolong Cui;Jie Liu","doi":"10.1029/2026RS008616","DOIUrl":"https://doi.org/10.1029/2026RS008616","url":null,"abstract":"Achieving an optimal balance between recognition accuracy and computational efficiency remains a pivotal challenge in millimeter-wave radar-based hand gesture recognition systems. In this paper, we propose a novel method that integrates a Dual-stream RepViT and Multi-teacher Knowledge Transfer Network (DRMKT-Net). The proposed dual-stream RepViT backbone effectively extracts spatiotemporal features from both Range-Time Maps and Doppler-Time Maps. On our custom data set with 22 gesture classes, the D-RepViT model achieves state-of-the-art recognition accuracy of 99.33%. Then, the model parameters are compressed, and, through a collaborative multi-teacher knowledge-transfer mechanism, the student model is reduced to only 27% of its original parameter count. Comparative experiments demonstrate that our approach significantly outperforms existing methods in terms of both recognition performance and computational efficiency. The proposed method exhibits promising potential for deployment in resource-constrained embedded devices for real-time human-computer interaction applications.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-18"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903098","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}

{"title":"An ultra-miniaturized meander-line implantable antenna for ISM-band WBAN applications with SAR analysis","authors":"N. Meenakshi;G. Yamuna;A. Babiyola","doi":"10.1029/2026RS008648","DOIUrl":"https://doi.org/10.1029/2026RS008648","url":null,"abstract":"This paper presents the creation of an ultra-miniaturized implanted meander lined antenna for Wireless Body Area Network (WBAN) applications. The employed antenna is especially intended for incorporation with implantable medical network, and it functions in the 2.45 GHz covering the Industrial, Scientific, and Medical (ISM) frequency range. In order to extend the electrical length of the proposed design, the meander line-like radiating components function as radiators and are connected to the ground section via a shorting pin. For improved impedance matching and compactness, the suggested antenna makes use of via (shorting pins), meander line configurations, and coaxial feedline. Extreme miniaturization, impedance matching within lossy biological tissues, radiation efficiency, and compliance with Specific Absorption Rate (SAR) safety guidelines are some of the significant challenges faced by implantable antennas that are specifically addressed by the proposed design. With the meander-line topology and shorting pins, the antenna can be made smaller while maintaining dependable performance for biomedical implant applications. The antenna's minimal overall tiny size of 4 × 4 × 0.5 mm³ allow it to be incorporated into modern medical and compact appliances. The antenna has been evaluated in tissues using an actual human body phantom simulator and at various levels. The suggested antenna was constructed, optimized, and modeled with the layers of skin, fat, liver, muscle, and brain phantom in account. Additionally, the antenna's SAR is determined and examined at both 1 and 10 g conditions. With the maximum permitted power input of 6.17 mW (1 g) and 36.3 mW (10 g) at 2.42 GHz, the SAR values are within the safety standards. The suggested antenna facilitates an energy-efficient solution and runs at low power levels. Biomedical applications can benefit from this small, minimized implanted antenna.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-13"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903099","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}

{"title":"Trust: A unified attention-based and uncertainty-aware framework for brain tumor detection and grading","authors":"K. Mohana Sundaram;R. Sasikumar","doi":"10.1029/2026RS008697","DOIUrl":"https://doi.org/10.1029/2026RS008697","url":null,"abstract":"Artificial intelligence (AI) system design for brain tumor diagnosis by utilizing Magnetic Resonance Imaging (MRI) demands more than accuracy; it also entails the development of robust, understandable, and medically trustworthy systems capable of handling heterogeneous imaging situations. The existing models are usually task-oriented, that is, either segmenting or classifying brain tumors in MRI images, and cannot easily generalize when faced with images from other machines and procedures. With the goal of tackling these limitations, this research seeks to develop the TRUST Brain Intelligence Framework. This proposed model is a unified architecture integrating Adaptive Contrast Harmonizer, attention-enhanced DeepLabV3+ segmentation, EfficientNetV2-based Scale Fusion Grader, Monte Carlo Dropout uncertainty estimation, and Grad-CAM++ explainability. Entropy-driven pre-processing enhances intensity consistency and tumor boundary preservation, whereas attention-guided segmentation and adaptive multi-scale grading facilitate discriminative feature learning. Empirical results using the BRISC and Brain Tumor MRI data sets reveal that the proposed approach significantly outperforms traditional approaches based on convolutional neural networks and segmentation. The proposed model was found to be highly effective in terms of Dice, Intersection Over Union, accuracy, and Fl-score, and it exhibited consistent performance across heterogeneous MRI modalities. Uncertainty-aware predictions and visual explanations further improved clinical interpretation of the results, making the framework more suitable for trustworthy AI-assisted neuro-oncology decision support.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-33"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903171","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}

{"title":"Flexible trident foam antenna with narrowband characterization for NB-IoT and LTE cellular communications","authors":"R. Ramyea;Senthil Kumar Kandasamy","doi":"10.1029/2026RS008636","DOIUrl":"https://doi.org/10.1029/2026RS008636","url":null,"abstract":"With the rapid expansion of LTE (Long Term Evolution) cellular and IoT (Internet of Things) enabled systems, there is a growing demand for compact, low-cost and flexible antennas. Present antennas are commonly built using rigid substrates which are not suitable for flexible applications and offers more signal reflection rather than far field radiation. Proposed work addresses this demand by a lightweight foam substrate based flexible antenna that operates at 1.74 GHz LTE-band 4 and additional 1.4 GHz LTE—band 11 to support (Narrow Band) NB-IoT applications. A trident shaped antenna built using foam with 1.2 mm thickness and permittivity of 1.15. Stagewise analysis in terms of electrical and geometrical is focused to improvize current distribution, radiation characteristics with lesser reflections. Gain and radiation efficiency of about 3.9 dB and 90.6% is achieved with the final stage antenna, with an impedance bandwidth of 570 MHz. Simulated results are validated with the measured results using vector network analyzer and anechoic chamber. Simulated and measured return loss is about — 42.3 and—31 dB respectively. To verify the flexibility and wearability of the antenna, conformal and SAR simulations are performed and analyzed for the real time deployment in flexible IoT and LTE cellular applications.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-13"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903044","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}

{"title":"HELIOS — Highly reliable links during solar conjunctions","authors":"A. Zeqaj;P. Tortora;E. Paolini;A. J. Stocker;D. R. Siddle;A. Argyriou;J. De Vicente;R. Abello;M. Mercolino","doi":"10.1029/2025RS008358","DOIUrl":"https://doi.org/10.1029/2025RS008358","url":null,"abstract":"During deep space missions, maintaining reliable communication between a spacecraft and Earth becomes particularly challenging during superior solar conjunctions, when the spacecraft passes behind the Sun relative to Earth. The highly ionized solar corona and solar wind create plasma inhomogeneities that severely affect radio signals, leading to phase scintillation, amplitude fading, and signal loss. These effects intensify as the Sun-Earth-Probe (SEP) angle decreases, resulting in frequent disruption of phase-locking techniques crucial for successful signal demodulation. This paper comprehensively analyzes the communication subsystem to ensure reliable tracking, telemetry, and command (TT&C) links during superior solar conjunctions. By analyzing the effects of solar plasma on radio links, the paper proposes new operational methods and subsystem architectures that enhance the robustness of RF communication even in very harsh conditions. The solutions include modulation, coding, non-coherent demodulation methods, and alternative channel models to mitigate scintillation effects and maintain stable communication links, particularly at low SEP angles. These strategies offer promising ways to improve data transmission reliability and maximize mission success during challenging solar conjunction phases.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-16"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148902721","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}

{"title":"Signal data stream parameters passing ionospheric communication links with fading caused by natural clutter phenomena","authors":"I. Bronfman;Y. Ben-Shimol;N. Blaunstein","doi":"10.1029/2025RS008518","DOIUrl":"https://doi.org/10.1029/2025RS008518","url":null,"abstract":"This paper explores the impact of natural phenomena on signal data transmission across various ionospheric communication channels. The study focuses on three primary phenomena: meteor trails prevalent in the middle- and lower-latitude ionosphere, bubble and plume structures observed around the equatorial ionosphere, and magnetic-storm-induced plasma structures excited at higher latitudes. These phenomena contribute substantially to two types of fast fading: flat and frequency-selective. The relationships between signal intensity, signal intensity scintillation index, and the ř-factor of fast frequency-selective fading are analytically derived. The mutual spectral characteristics of these parameters are also analyzed, considering their dependence on the carrier frequency of signals passing through channels affected by fading caused by natural clutter phenomena. Furthermore, the paper investigates the close relationship between the K-factor of fast fading, which characterizes multiplicative noise, and data stream parameters such as capacity, spectral efficiency, and bit error rate. The effects of natural clutter phenomena on signal data transmission are analyzed across various ionospheric communication channels with fading at different latitudes. The study considers two practical frequency bands: HF (3–50MHz), commonly used for “ionospheric weather” monitoring and ionospheric radiolocation using ionosondes, and UHF/SHF (1–60 GHz) typically employed for land-satellite communication links.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-16"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148902777","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}

{"title":"Achieving ship target detection in radar images via dual-route feature extraction and adjacent-layer feature fusion","authors":"Zhuoran Shi;Shichao Chen;Ming Liu;Shanshan Lu;Lei Yang;Ling Wang","doi":"10.1029/2026RS008649","DOIUrl":"https://doi.org/10.1029/2026RS008649","url":null,"abstract":"Focusing on the problem of balancing computational cost and detection accuracy in marine SAR image target detection, we propose a lightweight method based on Dual Route Feature Extraction and Adjacent-Layer Feature Fusion, which mainly consists of two steps. Firstly, we designed a dual-route feature extraction backbone, input features are equally divided in channel dimension, and feature extraction is carried out separately, which reduces the computational parameters. Meanwhile, to address the diversity of ship scales and rotation angles on the marine surface, deformable convolution is incorporated into the backbone, skip connection is used to enhance the information of small ship targets. Subsequently, in the feature fusion part, in order to reduce the damage caused by non-linear operations to the hierarchical correlation of the feature pyramid, a strategy of Adjacent-Layer Feature Fusion is adopted, and the feature output with a pyramidlike structure is generated. Experiments have proven that the constructed structure can maintain detection accuracy and reduce the computational cost of the network. The publicly available SSDD and HRSID are used to verify the advantage of the network. The experiments show that the network structure designed can effectively reduce the computational cost of the network while maintaining a relatively high detection accuracy.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 8","pages":"1-14"},"PeriodicalIF":1.6,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903046","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}

{"title":"Bregman wave distribution function method","authors":"Ryosei Nakazawa;Mamoru Ota;Yoshiya Kasahara","doi":"10.1029/2025RS008535","DOIUrl":"https://doi.org/10.1029/2025RS008535","url":null,"abstract":"This study proposes a wave distribution function (WDF) estimation method based on minimizing the Bregman divergence in the function space. The proposed method is entirely data-driven and requires no hyperparameter tuning during the estimation process. It can be regarded as an extension of the maximum entropy method. Whitening the spectral matrix was found to significantly enhance the estimation accuracy. By replacing the likelihood or loss function of the spectral matrix with its whitened counterpart, the estimated solutions were significantly improved. This method enables the precise estimation of WDFs from electromagnetic field observations, establishing a technical foundation for diagnosing space plasma environments and forecasting space weather. To address the uncertainty arising from the limited snapshots, we derive the posterior distribution of the spectral matrix. The Bregman divergence-based framework ensures stable and interpretable estimation under both physical and statistical constraints. Numerical experiments confirmed that whitening markedly improved both accuracy and robustness in realistic random wave scenarios.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"61 7","pages":"1-19"},"PeriodicalIF":1.6,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148675941","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}