Zenith tropospheric delay (ZTD) is an important atmospheric parameter in radio-space-geodetic techniques such as Global Navigation Satellite System (GNSS), which is pivotal for GNSS positioning, navigation and meteorology. The Vienna Mapping Function (VMF) data server is a widely utilized source for implementing ZTD, offering two types of models, that is, the empirical one and the discrete one with Grid-wise and Site-wise models. Therefore, to evaluate the accuracy of these models becomes the focus of this article. Specifically, this study investigates their performances in terms of calculation of ZTD, using the hourly values derived from the International GNSS Service data as references. The results show that the root mean square err (RMSE) of the Site-wise, Grid-wise and global pressure and temperature 3 model are 11.71/13.03/38.56 mm, respectively, indicating the discrete model performs generally better than the empirical model, and the Site-wise model is the better of the two discrete models. From the perspective of spatial resolution, the performance of these three models in ZTD calculation shows obvious influences of latitude changes and elevation differences. From the temporal analysis, the accuracy of the discrete model shows differences over different UTC epochs, while the empirical model can only express the seasonal ZTD characteristics with the average RMSE at different epochs being similar, the specifically values are 39.67, 39.26, 39.38 and 39.18 mm at UTC 0:00, 6:00, 12:00 and 18:00, respectively. The histogram and boxplot well indicate the accuracy differences of the three models in different seasons. Additionally, the time series of three models at different latitudes were also explored in this research. These explorations are conducive to the selection of appropriate models for calculating ZTD based on specific requirements.
{"title":"Comparing discrete and empirical troposphere delay models: A global IGS-based evaluation","authors":"Yifan Yao;Fei Yang;Jian Li;Lei Wang;Junxi Zheng;Ruixian Hao;Tairan Xu","doi":"10.1029/2024RS007950","DOIUrl":"10.1029/2024RS007950","url":null,"abstract":"Zenith tropospheric delay (ZTD) is an important atmospheric parameter in radio-space-geodetic techniques such as Global Navigation Satellite System (GNSS), which is pivotal for GNSS positioning, navigation and meteorology. The Vienna Mapping Function (VMF) data server is a widely utilized source for implementing ZTD, offering two types of models, that is, the empirical one and the discrete one with Grid-wise and Site-wise models. Therefore, to evaluate the accuracy of these models becomes the focus of this article. Specifically, this study investigates their performances in terms of calculation of ZTD, using the hourly values derived from the International GNSS Service data as references. The results show that the root mean square err (RMSE) of the Site-wise, Grid-wise and global pressure and temperature 3 model are 11.71/13.03/38.56 mm, respectively, indicating the discrete model performs generally better than the empirical model, and the Site-wise model is the better of the two discrete models. From the perspective of spatial resolution, the performance of these three models in ZTD calculation shows obvious influences of latitude changes and elevation differences. From the temporal analysis, the accuracy of the discrete model shows differences over different UTC epochs, while the empirical model can only express the seasonal ZTD characteristics with the average RMSE at different epochs being similar, the specifically values are 39.67, 39.26, 39.38 and 39.18 mm at UTC 0:00, 6:00, 12:00 and 18:00, respectively. The histogram and boxplot well indicate the accuracy differences of the three models in different seasons. Additionally, the time series of three models at different latitudes were also explored in this research. These explorations are conducive to the selection of appropriate models for calculating ZTD based on specific requirements.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141397724","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}
Tomoe Taki;Satoshi Kurita;Hirotsugu Kojima;Yoshiya Kasahara;Shoya Matsuda;Ayako Matsuoka;Yoichi Kazama;Chae-Woo Jun;Shiang-Yu Wang;Sunny W. Y. Tam;Tzu-Fang Chang;Bo-Jhou Wang;Yoshizumi Miyoshi;Iku Shinohara
We have analyzed Electrostatic Electron Cyclotron Harmonic (ECH) waves observed using interferometry observation mode performed by the Arase satellite to estimate low-energy electron temperatures. Interferometry can be used to calculate velocities, but the Arase satellite can only perform interferometry observations in a one-dimensional direction. We proposed a method to estimate the wave vector of the observed ECH waves from the observed electric fields and calculated the phase velocity for each frequency. We determined the particle parameters from the particle detector and the upper hybrid resonance and estimated the unknown low-energy electron temperature from the agreement between the observed ECH dispersion relation and the theoretical dispersion curves. We performed our analysis for six events and found that the low-energy electron temperature in the observed region is on the order of 1 eV.
{"title":"Cold electron temperature in the inner magnetosphere estimated through the dispersion relation of ECH waves from the Arase satellite observations","authors":"Tomoe Taki;Satoshi Kurita;Hirotsugu Kojima;Yoshiya Kasahara;Shoya Matsuda;Ayako Matsuoka;Yoichi Kazama;Chae-Woo Jun;Shiang-Yu Wang;Sunny W. Y. Tam;Tzu-Fang Chang;Bo-Jhou Wang;Yoshizumi Miyoshi;Iku Shinohara","doi":"10.1029/2023RS007927","DOIUrl":"10.1029/2023RS007927","url":null,"abstract":"We have analyzed Electrostatic Electron Cyclotron Harmonic (ECH) waves observed using interferometry observation mode performed by the Arase satellite to estimate low-energy electron temperatures. Interferometry can be used to calculate velocities, but the Arase satellite can only perform interferometry observations in a one-dimensional direction. We proposed a method to estimate the wave vector of the observed ECH waves from the observed electric fields and calculated the phase velocity for each frequency. We determined the particle parameters from the particle detector and the upper hybrid resonance and estimated the unknown low-energy electron temperature from the agreement between the observed ECH dispersion relation and the theoretical dispersion curves. We performed our analysis for six events and found that the low-energy electron temperature in the observed region is on the order of 1 eV.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141399064","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 presents the first ever observations on aspect-sensitive characteristics of 205 MHz stratosphere-troposphere (ST) radar located at a tropical station Cochin (10.04°N, 76.3°E) using volume scanning. The most significant and new observation is that the signal-to-noise ratio in zenith and off-zenith beams are nearly equal in some height region, indicating the presence of isotropic turbulence. Signal strength decreases by 0.75 dB per degree from 0 to 10 degree off-zenith, 0.9 dB per degree from 10 to 20 degree off-zenith and 0.3 dB per degree beyond 20 degree off-zenith. Different causative mechanisms are discussed on the basis of various estimated parameters associated with aspect sensitivity. Maximum aspect sensitivity is observed between 12 and 17 km, indicating the presence of dynamic instability arising due to strong wind shear and atmospheric stability. When both the square of wind shear and stability parameters are above 0.25 × 10 −3 s −2 , the scatterers become mostly isotropic. The study also shows a power difference in the symmetric beams as well as azimuth angle dependency. Analysis suggests that this asymmetry is due to the tilting of layers by the action of atmospheric gravity waves generated through Kelvin-Helmholtz instability. The present configuration of radar can provide a better understanding of three-dimensional structures of turbulence and instabilities.
{"title":"Structures and backscattering characteristics of CUSAT 205 MHz stratosphere-troposphere radar at Cochin (10.04°N, 76.3°E)—first results","authors":"Nabarun Poddar;Siddarth Shankar Das;Veenus Venugopal;S. Abhilash;V. Rakesh","doi":"10.1029/2023RS007894","DOIUrl":"10.1029/2023RS007894","url":null,"abstract":"This paper presents the first ever observations on aspect-sensitive characteristics of 205 MHz stratosphere-troposphere (ST) radar located at a tropical station Cochin (10.04°N, 76.3°E) using volume scanning. The most significant and new observation is that the signal-to-noise ratio in zenith and off-zenith beams are nearly equal in some height region, indicating the presence of isotropic turbulence. Signal strength decreases by 0.75 dB per degree from 0 to 10 degree off-zenith, 0.9 dB per degree from 10 to 20 degree off-zenith and 0.3 dB per degree beyond 20 degree off-zenith. Different causative mechanisms are discussed on the basis of various estimated parameters associated with aspect sensitivity. Maximum aspect sensitivity is observed between 12 and 17 km, indicating the presence of dynamic instability arising due to strong wind shear and atmospheric stability. When both the square of wind shear and stability parameters are above 0.25 × 10\u0000<sup>−3</sup>\u0000 s\u0000<sup>−2</sup>\u0000, the scatterers become mostly isotropic. The study also shows a power difference in the symmetric beams as well as azimuth angle dependency. Analysis suggests that this asymmetry is due to the tilting of layers by the action of atmospheric gravity waves generated through Kelvin-Helmholtz instability. The present configuration of radar can provide a better understanding of three-dimensional structures of turbulence and instabilities.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141404745","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}
L. Poli;P. Rocca;P. Rosatti;N. Anselmi;M. Salucci;S. Yang;F. Yang;A. Massa
In this paper, the design of a novel horizontally polarized single-layer antenna for 77 (GHz) automotive radar applications is4 addressed. An innovative non-uniform zig-zag parametrization of the antenna layout is considered to enable a more flexible control on both the impedance matching in the working frequency band and the shaping of the radiated beam pattern with respect to a standard (uniform) one without compromising the linear (horizontal) polarization of the radiated field. Such a polarization guarantees a lower back-scattering from road pavements, resulting in a reduced amount of clutter and thus allowing a more robust target detection. Moreover, the single-layer layout has several advantages in terms of fabrication simplicity/costs and mechanical robustness to vibrations. The design of the proposed non-uniform zig-zag antenna (NZA) is performed through a customized implementation of the System-by-Design (SbD) approach that fruitfully combines machine learning and evolutionary optimization to efficiently deal with the computational complexity at hand. An extensive numerical validation, dealing with designs of different lengths, verifies the high performance of the NZA in terms of beam direction deviation (e.g., BDD < 1 (deg)), sidelobe level (e.g., SLL < —18.2 (dB)), and polarization ratio (e.g., PR > 20 (dB)) within the working frequency band H = [76 : 78] (GHz), as well as its superiority over competitive designs. Finally, the realization of a prototype and its experimental test, validate the proposed NZA concept for automotive mm-wave radar applications in advanced driver assistance systems and autonomous vehicles such as, for instance, adaptive cruise control, collision avoidance, and blind spot detection.
{"title":"AI-assisted design of printed edge-fed non-uniform ZigZag antenna for mm-wave automotive radar","authors":"L. Poli;P. Rocca;P. Rosatti;N. Anselmi;M. Salucci;S. Yang;F. Yang;A. Massa","doi":"10.1029/2023RS007912","DOIUrl":"https://doi.org/10.1029/2023RS007912","url":null,"abstract":"In this paper, the design of a novel horizontally polarized single-layer antenna for 77 (GHz) automotive radar applications is4 addressed. An innovative non-uniform zig-zag parametrization of the antenna layout is considered to enable a more flexible control on both the impedance matching in the working frequency band and the shaping of the radiated beam pattern with respect to a standard (uniform) one without compromising the linear (horizontal) polarization of the radiated field. Such a polarization guarantees a lower back-scattering from road pavements, resulting in a reduced amount of clutter and thus allowing a more robust target detection. Moreover, the single-layer layout has several advantages in terms of fabrication simplicity/costs and mechanical robustness to vibrations. The design of the proposed non-uniform zig-zag antenna (NZA) is performed through a customized implementation of the System-by-Design (SbD) approach that fruitfully combines machine learning and evolutionary optimization to efficiently deal with the computational complexity at hand. An extensive numerical validation, dealing with designs of different lengths, verifies the high performance of the NZA in terms of beam direction deviation (e.g., BDD < 1 (deg)), sidelobe level (e.g., SLL < —18.2 (dB)), and polarization ratio (e.g., PR > 20 (dB)) within the working frequency band H = [76 : 78] (GHz), as well as its superiority over competitive designs. Finally, the realization of a prototype and its experimental test, validate the proposed NZA concept for automotive mm-wave radar applications in advanced driver assistance systems and autonomous vehicles such as, for instance, adaptive cruise control, collision avoidance, and blind spot detection.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495249","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}
Rajnish K. Ranjan, Atanu Chowdhury, Dibyendu Ghoshal
The practical applications within the domain of the fifth generation (5G) and the emerging beyond 5G network necessitate a high data transmission rate along with minimal achievable delay. With this objective in focus, the maximum capacity is extensively quantified through the utilization of the delay-constrained effective capacity (EC) technique, which stands in contrast to Shannon's ergodic capacity. The current study is engaged in the analysis of EC within a delay-limited wireless system operating in a double-shadowed Rician (DSR) fading channel. Within this channel, only the Nakagami-m distribution concept has been applied to both the dominant and secondary shadowing components of the proposed network model. A new exact closed-form expression for EC within the DSR fading channel has been derived using the Fox-H function. Furthermore, an analysis has been conducted for both high and low signal-to-noise ratios to provide further insights and explanations for the proposed model. It is worth noting that the results obtained from both simulation and analytical methods exhibit substantial similarity, revealing interdependence among various parameters present in the proposed model.
{"title":"On The Effective Capacity Performance Analysis Over Nakagami-m Distribution-Based Double-Shadowed Rician Fading Channel","authors":"Rajnish K. Ranjan, Atanu Chowdhury, Dibyendu Ghoshal","doi":"10.1029/2023rs007868","DOIUrl":"https://doi.org/10.1029/2023rs007868","url":null,"abstract":"The practical applications within the domain of the fifth generation (5G) and the emerging beyond 5G network necessitate a high data transmission rate along with minimal achievable delay. With this objective in focus, the maximum capacity is extensively quantified through the utilization of the delay-constrained effective capacity (EC) technique, which stands in contrast to Shannon's ergodic capacity. The current study is engaged in the analysis of EC within a delay-limited wireless system operating in a double-shadowed Rician (DSR) fading channel. Within this channel, only the Nakagami-<i>m</i> distribution concept has been applied to both the dominant and secondary shadowing components of the proposed network model. A new exact closed-form expression for EC within the DSR fading channel has been derived using the Fox-H function. Furthermore, an analysis has been conducted for both high and low signal-to-noise ratios to provide further insights and explanations for the proposed model. It is worth noting that the results obtained from both simulation and analytical methods exhibit substantial similarity, revealing interdependence among various parameters present in the proposed model.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598971","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}
Science operates best by sharing accurate new knowledge in clear ways. To check our assumptions, our methods, and our interpretations of the observations, experiments, analyses, and calculations that we do, we ask experts who were not involved in the study to critically evaluate our work. We call this peer review. They look for completeness, accuracy, whether work is new, and how clearly we have written the descriptions. We continue to be humbled by the time, effort, and careful insights that our colleagues share with each other through the process of peer review. Thank you all for your efforts toward advancing radio science now and for the future.
Individuals in italics provided three or more reviews for Radio Science during the year.
{"title":"Thank You to Our 2023 Reviewers","authors":"Sana Salous, Kazuya Kobayashi","doi":"10.1029/2024rs008003","DOIUrl":"https://doi.org/10.1029/2024rs008003","url":null,"abstract":"<p>Science operates best by sharing accurate new knowledge in clear ways. To check our assumptions, our methods, and our interpretations of the observations, experiments, analyses, and calculations that we do, we ask experts who were not involved in the study to critically evaluate our work. We call this peer review. They look for completeness, accuracy, whether work is new, and how clearly we have written the descriptions. We continue to be humbled by the time, effort, and careful insights that our colleagues share with each other through the process of peer review. Thank you all for your efforts toward advancing radio science now and for the future.</p>\u0000<p>Individuals in italics provided three or more reviews for <i>Radio Science</i> during the year.</p>\u0000<p>A</p>\u0000<p>Aaron Chippendale</p>\u0000<p>Abid Khan</p>\u0000<p><i>Abubaker Elobied</i></p>\u0000<p>Adam Beardsley</p>\u0000<p>Adel Thaljaoui</p>\u0000<p>Adnan Cheema</p>\u0000<p>Agri Faturahman</p>\u0000<p><i>Aiswarya RS</i></p>\u0000<p>Ajeet Kumar</p>\u0000<p>Akimasa Hirata</p>\u0000<p>Alan E. E. Rogers</p>\u0000<p>Albane Saintenoy</p>\u0000<p>Alex Chartier</p>\u0000<p>Alex Minetto</p>\u0000<p>Alexander Shvets</p>\u0000<p>Alexei Dmitriev</p>\u0000<p><i>Alexey Oinats</i></p>\u0000<p>Ali Zidour</p>\u0000<p>Alireza Mahmoudian</p>\u0000<p>Alison Moraes</p>\u0000<p>Amir Rezagholi</p>\u0000<p><i>Amjad Iqbal</i></p>\u0000<p>Ana Elias</p>\u0000<p><i>Anand Kumar</i></p>\u0000<p>Andres Romero-Wolf</p>\u0000<p>Andrey Lyakhov</p>\u0000<p>Angelo De Santis</p>\u0000<p>Animesh Maitra</p>\u0000<p><i>Ankan Bhattacharya</i></p>\u0000<p>Ashik Paul</p>\u0000<p><i>Asif Ahmed</i></p>\u0000<p>Asma S</p>\u0000<p>Atsuki Shinbori</p>\u0000<p>Avinash Deshpande</p>\u0000<p>Axel von Engeln</p>\u0000<p><i>Ayman Althuwayb</i></p>\u0000<p>Balaji K</p>\u0000<p>Benjamin Reid</p>\u0000<p>Bing Li</p>\u0000<p>Bo Ai</p>\u0000<p>Brecht De Beelde</p>\u0000<p>Brent Page</p>\u0000<p>Brian Breitsch</p>\u0000<p>C Vedavathi</p>\u0000<p>Carlo Scotto</p>\u0000<p><i>Chandan Kumar Ghosh</i></p>\u0000<p>Chao Xiong</p>\u0000<p>Chaoxian Qi</p>\u0000<p>Charles Naudet</p>\u0000<p>Cherry Ng</p>\u0000<p><i>Chinmoy Bhattacharya</i></p>\u0000<p><i>Christina Arras</i></p>\u0000<p><i>Christopher Volk</i></p>\u0000<p>Conor Brennan</p>\u0000<p>Craig Rodger</p>\u0000<p>D Sarma Achanta</p>\u0000<p>Daban Kadhim Omar Dabbagh</p>\u0000<p>Dalia Nandi</p>\u0000<p>Daniel Greenway</p>\u0000<p>Daniel Kastinen</p>\u0000<p>Daniel Kouba</p>\u0000<p>Daniel Okoh</p>\u0000<p>Dariia Savelian</p>\u0000<p>Dario Bojanjac</p>\u0000<p>Dario Sabbagh</p>\u0000<p>Dave Laurenson</p>\u0000<p><i>David Hartley</i></p>\u0000<p><i>David Themens</i></p>\u0000<p>Dayang Li</p>\u0000<p>Deepak Singh</p>\u0000<p><i>Dinesh Jackson Samuel Samuel</i></p>\u0000<p>Dmitrii Solomitckii</p>\u0000<p>Dominique Lesselier</p>\u0000<p><i>Dustin Buccino</i></p>\u0000<p>Edmund Spencer</p>\u0000<p>Eduardo Araujo-Pradere</p>\u0000<p>Elnour Badria</p>\u0000<p>Enrico Testi</p>\u0000<p>Ercha Aa</p>\u0000<p>Euclides Chuma</p>\u0000<p>François Lavoué</p>\u0000<p>Gareth Chisham</p>\u0000<p>Gargi Rakshit</p>\u0000<p><i>Gerald Arada</i></p>\u0000<p><i>Giada Battaglia</i></p>\u0000<p><i>Giuseppe Mazzarella</i></p>\u0000<p>Glenn Hussey</p>\u0000<p><i>Guanyi Ma</i></p>\u0000<p>Gunter Stober</p>\u0000<p>Guobin Yang</p>\u0000<p><i>Guozhu Li</i></p>\u0000<p>H. Adenle</p>\u0000<p>Hai-Sheng Zhao</p>\u0000<p>Haiyang Fu</p>\u0000<p>Hector Garcia Martinez</p>\u0000<p><i>Heidi Morris</i></p>","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598983","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}
T. G. Cameron, R. A. D. Fiori, G. W. Perry, A. Spicher, T. Thayaparan
High latitude ionospheric density structures such as polar cap patches and arcs are capable of deflecting high frequency (HF) radio waves to off-great circle paths, and are likely detrimental to technologies dependent on HF radio propagation. In this study, nearly 2.5 years of 4.6–14.4 MHz data from a multi-frequency HF radio link between Qaanaaq, Greenland and Alert, Canada are used to investigate high-latitude off-great circle propagation in the polar cap. After an example of HF radio propagation affected by polar cap patches is shown in detail, a statistical analysis of the occurrence and impacts of off-great circle deflections in the polar cap is presented. Off-great circle propagation is shown to be increasingly common with increasing frequency up to 11.1 MHz, such that averaged over 1 year, received 11.1 MHz signals experienced deflections >30° from the great circle direction 65.6% of the time. The occurrence of these deflections across the year is shown to be at a maximum in the winter, while occurrence across the day varies with season. Trends across both time of day and time of year for 11.1 and 14.4 MHz deflections are consistent with polar cap patch occurrence trends. Off-great circle deflections are shown to be associated with increased time-of-flights, a larger range of positive and negative Doppler shifts, increased Doppler spreads, and lower signal-to-noise ratios. These results are discussed in the context of ionospheric phenomena in the polar cap, and implications for over-the-horizon radars operating at high latitudes.
{"title":"Statistical Analysis of Off-Great Circle Radio Wave Propagation in the Polar Cap","authors":"T. G. Cameron, R. A. D. Fiori, G. W. Perry, A. Spicher, T. Thayaparan","doi":"10.1029/2023rs007897","DOIUrl":"https://doi.org/10.1029/2023rs007897","url":null,"abstract":"High latitude ionospheric density structures such as polar cap patches and arcs are capable of deflecting high frequency (HF) radio waves to off-great circle paths, and are likely detrimental to technologies dependent on HF radio propagation. In this study, nearly 2.5 years of 4.6–14.4 MHz data from a multi-frequency HF radio link between Qaanaaq, Greenland and Alert, Canada are used to investigate high-latitude off-great circle propagation in the polar cap. After an example of HF radio propagation affected by polar cap patches is shown in detail, a statistical analysis of the occurrence and impacts of off-great circle deflections in the polar cap is presented. Off-great circle propagation is shown to be increasingly common with increasing frequency up to 11.1 MHz, such that averaged over 1 year, received 11.1 MHz signals experienced deflections >30° from the great circle direction 65.6% of the time. The occurrence of these deflections across the year is shown to be at a maximum in the winter, while occurrence across the day varies with season. Trends across both time of day and time of year for 11.1 and 14.4 MHz deflections are consistent with polar cap patch occurrence trends. Off-great circle deflections are shown to be associated with increased time-of-flights, a larger range of positive and negative Doppler shifts, increased Doppler spreads, and lower signal-to-noise ratios. These results are discussed in the context of ionospheric phenomena in the polar cap, and implications for over-the-horizon radars operating at high latitudes.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140599467","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 work studies variations of ionospheric total electron content (TEC) during four distinct solar eclipse events over the Ethiopia region. Dual-frequency global positioning system (GPS) data obtained from UNAVCO over Addis Ababa (9.036°N, 38.76°E) and Bahir Dar (11.6°N, 37.34°E) stations are used to examine the ionospheric variability during two annular solar eclipses on 15 January 2010 and 1 September 2016, a partial solar eclipse on 4 January 2011, and a hybrid solar eclipse (the eclipse path starts out as annular but later changes to total) on 3 November 2013. The results show a significant decrease in TEC values during the occurrence of the solar eclipses. Specifically, the TEC values are reduced to −20% and −10% during the annular eclipse on 15 January 2010, −33% and −38% during the partial solar eclipse on 4 January 2011, −26% and −24% during the annular solar eclipse on 1 September 2016, over the Addis Ababa and Bahir Dar stations, respectively. There is only minimal change in TEC of −8% and −9% at Addis Ababa and Bahir stations, respectively, during the 3 November 2013 solar eclipse even if the obstruction rate is high over the study area. Furthermore, the study shows that the spatial gradient of TEC reduction varies at different locations, which is attributed to the distinct amount of reduction in solar radiation reaching the Earth's surface, resulting in reduced photo-ionization. Overall, this study provides insightful information about the behavior of the ionospheric TEC during solar eclipses over Ethiopia and emphasizes the use of dual-frequency GPS data in tracking the variations of the TEC.
{"title":"Variation in Total Electron Content Over Ethiopia During the Solar Eclipse Events","authors":"Chali Idosa Uga, Sujan Prasad Gautam, Uluma Edward, Binod Adhikari, Dessalegn Teferi, Ashutosh Giri, Athwart Davis Odhiambo, Ayomide Olabode","doi":"10.1029/2023rs007830","DOIUrl":"https://doi.org/10.1029/2023rs007830","url":null,"abstract":"This work studies variations of ionospheric total electron content (TEC) during four distinct solar eclipse events over the Ethiopia region. Dual-frequency global positioning system (GPS) data obtained from UNAVCO over Addis Ababa (9.036°N, 38.76°E) and Bahir Dar (11.6°N, 37.34°E) stations are used to examine the ionospheric variability during two annular solar eclipses on 15 January 2010 and 1 September 2016, a partial solar eclipse on 4 January 2011, and a hybrid solar eclipse (the eclipse path starts out as annular but later changes to total) on 3 November 2013. The results show a significant decrease in TEC values during the occurrence of the solar eclipses. Specifically, the TEC values are reduced to −20% and −10% during the annular eclipse on 15 January 2010, −33% and −38% during the partial solar eclipse on 4 January 2011, −26% and −24% during the annular solar eclipse on 1 September 2016, over the Addis Ababa and Bahir Dar stations, respectively. There is only minimal change in TEC of −8% and −9% at Addis Ababa and Bahir stations, respectively, during the 3 November 2013 solar eclipse even if the obstruction rate is high over the study area. Furthermore, the study shows that the spatial gradient of TEC reduction varies at different locations, which is attributed to the distinct amount of reduction in solar radiation reaching the Earth's surface, resulting in reduced photo-ionization. Overall, this study provides insightful information about the behavior of the ionospheric TEC during solar eclipses over Ethiopia and emphasizes the use of dual-frequency GPS data in tracking the variations of the TEC.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140598968","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}
Statistical analysis of the temporal and spatial variations in the ionosphere is necessary to improve the shortwave system. Based on the standardized Euclidean distance algorithm, multisource ionospheric assimilation data, International GNSS Service vertical total electron content data, and ionosonde data are used to statistically analyze the ionospheric correlation distance, and the variation of ionospheric correlation distances with local times, magnetic latitudes, and seasons are obtained. The statistical analysis results show that the zonal ionospheric correlation distance presents minima in the equatorial ionospheric anomaly crest regions. Additionally, the meridional correlation distance in middle magnetic latitudes is greater than that in other regions. The zonal ionospheric correlation distance presents obvious local‐time variability. The variation trends of the meridional and zonal correlation distance during spring and autumn are similar. The patterns of the ionospheric correlation range variation with local times, magnetic latitudes, and seasons can be used to select the optimal locations or spacing for ionosonde stations, shortwave multi‐station systems, and shortwave radio beacons.
{"title":"Statistical Analysis of Ionospheric Correlation for Shortwave System","authors":"Mingjie Lv, Qiong Tang, Jiandong Qiao, Wei Qiao, Chen Zhou","doi":"10.1029/2023rs007893","DOIUrl":"https://doi.org/10.1029/2023rs007893","url":null,"abstract":"Statistical analysis of the temporal and spatial variations in the ionosphere is necessary to improve the shortwave system. Based on the standardized Euclidean distance algorithm, multisource ionospheric assimilation data, International GNSS Service vertical total electron content data, and ionosonde data are used to statistically analyze the ionospheric correlation distance, and the variation of ionospheric correlation distances with local times, magnetic latitudes, and seasons are obtained. The statistical analysis results show that the zonal ionospheric correlation distance presents minima in the equatorial ionospheric anomaly crest regions. Additionally, the meridional correlation distance in middle magnetic latitudes is greater than that in other regions. The zonal ionospheric correlation distance presents obvious local‐time variability. The variation trends of the meridional and zonal correlation distance during spring and autumn are similar. The patterns of the ionospheric correlation range variation with local times, magnetic latitudes, and seasons can be used to select the optimal locations or spacing for ionosonde stations, shortwave multi‐station systems, and shortwave radio beacons.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140764226","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}
J. M. E. Geerarts;G. Theis;A. B. Smolders;D. Caratelli
State-of-the-art conformal array pattern synthesis techniques typically suffer from a significant computational burden. This article builds upon the auxiliary array pattern synthesis technique, allowing the technique to work on elliptical contours. This deterministic method is both computationally efficient and capable of handling complex design cases with additional design constraints. In order to highlight the versatility and applicability, the method has been applied to an elliptical arc array comprised of Rampart antennas and an elliptical ring array using dipole elements. The results have been validated through full-wave electromagnetic simulations, as well as physical measurements. Both arrays presented show good agreement with the proposed synthesis technique. Highlighting the ability to satisfy additional design constraints, such as enforcing a minimal element spacing or having a controlled beamformer-network complexity.
{"title":"Synthesis of elliptically shaped aperiodic antenna arrays subject to complex design constraints","authors":"J. M. E. Geerarts;G. Theis;A. B. Smolders;D. Caratelli","doi":"10.1029/2023RS007914","DOIUrl":"10.1029/2023RS007914","url":null,"abstract":"State-of-the-art conformal array pattern synthesis techniques typically suffer from a significant computational burden. This article builds upon the auxiliary array pattern synthesis technique, allowing the technique to work on elliptical contours. This deterministic method is both computationally efficient and capable of handling complex design cases with additional design constraints. In order to highlight the versatility and applicability, the method has been applied to an elliptical arc array comprised of Rampart antennas and an elliptical ring array using dipole elements. The results have been validated through full-wave electromagnetic simulations, as well as physical measurements. Both arrays presented show good agreement with the proposed synthesis technique. Highlighting the ability to satisfy additional design constraints, such as enforcing a minimal element spacing or having a controlled beamformer-network complexity.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141041697","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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