Scholarly Publications
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This community showcases the academic contributions of faculty and researchers at Banaras Hindu University (BHU) and provides a year-wise compilation of publications across disciplines. Institutional Repository BHU
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PublicationArticle Study of ionospheric response to an intense geomagnetic storm of 26 August 2018 over low latitudes and polar regions(Elsevier Ltd, 2025) Uma S. Pandey; S. Veeresh J. Kumar; Javed N. Malik; Anil Kumar SinghDuring, the minimum phase of Solar Cycle 24, an intense geomagnetic storm occurred on August 26, 2018. This storm is significant not only because of its extremely high magnetic activity but also due to its great impact on the geo-magnetosphere. The aim of this paper is to distinguish the response of the equatorial/low latitude ionosphere to geomagnetic storms from those observed in the polar ionosphere. The ionospheric response to this storm has been investigated using 14 GPS receivers at the low latitudes and polar regions in the Asian and Antarctic sectors. Analysis of GPS-TEC data during the geomagnetic storm found both positive and negative storm effects over low and polar latitudes. The enhancement in VTEC data before the commencement of the geomagnetic storm is observed over all the stations at low latitude and polar regions, which is attributed to the pre-storm solar-induced events like CMEs, and proton events. Observed geomagnetic storm effects at different longitude sectors, whether it is positive or negative, are discussed using prompt penetration of electric field, disturbance dynamo electric field, neutral wind composition changes, and storm-induced wind lifting effects. During the recovery phase on 27–28, August the positive storm effect is noticed in daytime hours at equatorial/low latitude stations, whereas the negative storm effect as in the polar region. © 2025 Elsevier LtdPublicationBook Chapter Appraisal of spatial interpolation techniques in predicting soil organic carbon using earth observation datasets(Elsevier, 2024) Prachi Singh; Pashupati Nath Singh; Swati Srivastava; Sudha Suman; Prashant K. SrivastavaNumerous soil characteristics are influenced by soil organic carbon (SOC), including nutrient and water-holding capacity, nitrogen cycling and stability, enhanced water infiltration and aeration. Additionally, it is a vital factor in determining the condition of the soil, which is suited for agricultural output. Due to the physical difficulties of surveying in the natural environment, SOC mapping is a challenging procedure that is expensive and time-consuming, especially for large, heterogeneous surfaces. Presented chapter employed GPS-assisted and remote sensing-based studies to compare the usefulness of four commonly used interpolation algorithms for estimating soil moisture such as Inverse Distance Weighting (IDW), Spline, Ordinary Kriging models, and Kriging with External Drift (KED) interpolation approaches were discussed. This chapter also discussed the appraisal of soil moisture distribution using the various GIS spatial interpolation techniques to know the relationship between soil characteristics. Nowadays advanced remote sensing devices such as radiometer and earth observation datasets are vital sources and tools for the estimation of soil organic carbon at the local or regional scale. © 2025 Elsevier Ltd. All rights reserved.PublicationArticle Observed (GPS) and modeled (IRI and TIE-GCM) TEC trends over southern low latitude during solar cycle-24(Elsevier Ltd, 2023) S.S. Rao; Monti Chakraborty; A.K. SinghThe Total Electron Content (TEC) derived from the Global Positioning System (GPS) measurements during the solar cycle-24 at COCO Island (12.20⁰ S, 96.80⁰ E) are compared with those of International Reference Ionosphere-2016 (IRI-2016) model and Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM). TEC data derived from the above two models follow the nature of observed variations with considerable divergences in amplitudes. The precision of model TEC in reference to GPS TEC is discussed using a correlation coefficient, mean difference, root mean square error, and relative deviation module mean techniques. The randomness of predictions is found to be biased by the solar cycle, season, and local time. The simulated values showed better accuracy during the low solar activity and night hours. This study is an extension of Rao et al. (2019b), in which we reported similar study of TEC variability at the northern low latitude station. First of all, it is observed from two studies that the magnitude of TEC is greater at the southern low latitude than at the northern low latitude. Also the correlation between GPS TEC/ IRI TEC and F10.7 flux is determined to be greater at northern low latitude station compared to southern low latitude station. However, TIE-GCM TEC values are found to be slightly more correlated with F10.7 flux at southern low latitude station compared to northern low latitude station. With regard to seasonal variation, semiannual oscillations in TEC are found to be coherent on both sides of the equator. However, the winter anomaly is not observed or predicted by models at the southern low latitude whereas it is observed to be a solar flux-dependent feature at the northern low latitude. The IRI model closely follows seasonal trends of TEC whereas TIE-GCM over-predicted TEC during solstices at the northern low latitudes. Models TEC deviations are found to be lesser at the southern low latitude compared to northern low latitude. © 2022 COSPARPublicationArticle Analysis of GPS-TEC and IRI model over equatorial and EIA stations during solar cycle 24(Elsevier Ltd, 2023) Sunil Kumar Chaurasiya; Kalpana Patel; Sanjay Kumar; Abhay Kumar SinghTotal Electron Content (TEC) measurements provided by Global Positioning System (GPS) as well as the International Reference Ionosphere – 2016 model (IRI01-Corr, IRI-2001, and NeQuick) model were compared at two Indian GPS stations: equatorial station Bangalore (12.580N, 77.350 E) and equatorial ionization anomaly (EIA) station Lucknow (26.500N, 80.550 E) during the solar cycle 24 extending from 2007 to 2017. The spectral, regression and statistical analysis displays a double-hump shape with counterclockwise hysteresis within TEC. The solar flux along with the TEC showed erratic as well as sluggish trends throughout the increasing period and flat and rapid throughout the decreasing period of the solar cycle 24. The semiannual and winter anomaly is discovered to be a constant feature throughout the solar cycle. The main idea of the current study is to investigate the performance of IRI01-Corr, IRI-2001, and NeQuick TEC in contrast to GPS TEC data throughout solar cycle 24 at the Indian equatorial and EIA stations. The modeled TEC data exhibit almost complete agreement with the measurement highlighting the same trends in the solar cycle as well as semiannual and seasonal changes. However, there are clear biases between the observed and modeled TECs when local time, seasons, as well as solar activity phases are considered. The main findings of this paper are that the NeQuick model generally underestimates noon-time TEC while the IRI-2001 model overestimates the same. The error in estimating noontime TEC from the IRI model using IRI-2001 as a topside at the EIA station is higher (142 %) than that at the equatorial station (42 %). © 2023 COSPARPublicationBook Chapter Study of the atmospheric and ionospheric phenomenon using GPS-based remote sensing technique(Elsevier, 2022) Sanjay Kumar; S.S. Rao; Mukulika Mondal; A.K. SinghAtmosphere including the ionosphere acting as a threat to global positioning system (GPS) signals which can provide valuable information about content of the medium. Ionospheric and tropospheric delay measurements using dual frequency GPS computations made at L1 and L2 frequencies enable reliable estimation of the gradually varying ionospheric and atmospheric conditions and hence estimation of total electron content and water vapor, respectively. Our atmosphere and ionosphere are very much sensitive to several natural and hazardous events, such as earthquakes, thunderstorms, space weather, solar eclipse, cyclone, typhoon, sudden stratospheric warming, etc. In this chapter, influences, tracking, forecasting of hazardous events such as earthquakes, thunderstorms, solar eclipse, cyclone, typhoon, sudden stratospheric warming using data from ground-based GPS measurements will be discussed. Besides, the significance of water vapor as a greenhouse gas and global warming, weather phenomenon, and climate variation and its relevance in modern society will be also been discussed. Finally, scope and challenges of the above phenomenon using GPS-based measurements are discussed. © 2023 Elsevier Ltd. All rights reserved.PublicationBook Chapter Probing the upper atmosphere using GPS(Elsevier, 2021) S.S. Rao; A.K. SinghThe Global Positioning System satellites provide an extensive array of beacon signals at L-band frequencies (1.2 and 1.6GHz), which are used for satellite-based navigation, communication, and ground positioning. Before being received at the ground, these signals have to pass through the ionosphere. The ionosphere is a dispersive medium, whose variability affects the quality of the received signal, and is a matter of grave concern for civilian as well as military applications that rely on these signals. The ionospheric plasma density drastically changes during various solar (solar flare, corona mass ejection), astronomical (solar eclipse), and seismological (earthquake) phenomena. Understanding these processes is of great scientific value and has practical benefits in satellite-based communication and navigation. In this chapter, a brief overview on ionospheric weather and outcomes of studies on solar, astronomical, and terrestrial phenomena employed worldwide is discussed. © 2021 Elsevier Inc. All rights reserved.PublicationBook Chapter Probing the tropospheric water vapor using GPS(Elsevier, 2021) Sanjay Kumar; R.P. Singh; A.K. SinghThis chapter provides a brief introduction about Global Positioning System (GPS), its structures, and working principle with applications mainly to water vapor measurements. A brief introduction about signals transmitted from GPS satellites, signal structures, and their propagations from satellite to receiver has also been presented. During the signal propagation from satellite to receiver, several errors such as satellite clock error, ephemeris error, atmospheric error, multipath error, receiver noises are introduced in the signals, which have also been discussed. Atmosphere acts as a threat for Global Navigation Satellite System signal and provides valuable information about content of the medium. The presence of water vapor in addition to dry components such as oxygen and nitrogen degrades the GPS signal significantly, and its estimation gives information about water vapor content of the atmosphere. Usually, water vapor resides in the troposphere, and hence tropospheric error measurement in GPS signal is used to determine water vapor contents. Water vapor is an important component of global warming, weather phenomenon, numerical weather prediction (NWP), hydrological cycle, and climate variation, and hence its precise estimation is most relevant in modern society. For NWP point of view, tomographic modeling of water vapor with relevant accuracy is a challenging task. Finally, scope and challenges of water vapor measurement are discussed. © 2021 Elsevier Inc. All rights reserved.PublicationBook Chapter Future pathway for research and emerging applications in GPS/GNSS(Elsevier, 2021) Manish Kumar Pandey; Prashant K. Srivastava; George P. PetropoulosSatellite navigation system has an unparalleled advantage in navigational technologies due to its high-precision delivery of location in terms of position, time, and velocity on any object or person. It had found its application in the areas ranging from transportation, geodesic, communication, disaster prevention to its handling to security, etc., to name a few. This chapter provides an overview of the satellite navigation system and the associated vulnerabilities to explore the future pathway for research and emerging applications. This chapter begins with a brief introduction of the satellite navigation systems and briefly describes the constellations of the Global Navigation Satellite System (GNSS). The evolution of the GNSS is discussed along with its market emergence and convergence followed by a detailed discussion on the challenges and vulnerabilities of the GNSS. These challenges and vulnerabilities provide a pathway for future research and help the researchers in developing emerging applications. © 2021 Elsevier Inc. All rights reserved.PublicationBook Chapter Application of GPS and GNSS technology in geosciences(Elsevier, 2021) Pavan Kumar; Prashant K. Srivastava; Prasoon Tiwari; R.K. MallGlobal Positioning System (GPS) is a global navigational satellite system developed by the United States Department of Defense. This technology is available only with America, Russia (GLONASS), China (BeiDou), and Japan (Quasi-Zenith Satellite System). In this, the navigation systems of America and Russia are global, while countries like China and Japan are using it regionally. The European Union has also completed preparations to start its navigation system. In terms of surveying, mapping technology, and engineering construction, it is used not only in the establishment of Earth control networks but also in the establishment of land and ocean geodetic survey benchmarks. Global Navigation Satellite System (GNSS) framework is one of the four major positioning systems, mainly GPS, GLONASS, GNS, and BeiDou, in the world. This chapter describes the application of GPS and GNSS Technology in Geosciences like rescue and relief projects, agriculture, dynamic observation, time transmission, speed measurement, vehicle guidance, and other fields. © 2021 Elsevier Inc. All rights reserved.PublicationArticle Ionospheric perturbations observed due to Indonesian Earthquake (Mw = 7.4) using GPS and VLF measurements at multi-stations(Springer Science and Business Media B.V., 2021) Sanjay Kumar; Gaurish Tripathi; Pradeep Kumar; Ashutosh K. Singh; Abhay K. SinghIn the present paper Global Positioning System (GPS) as well as Very Low Frequency (VLF) measurements at multi-stations have been used to analyze ionospheric anomalies related with major earthquake (Mw = 7.4) of South West Banten (Lampung Area), Indonesia. The earthquake occurred on 02 August 2019 at 19:03:21 LT (epicenter at geog. lat = 07.22° S, long. 104.83º E, depth 10 km). Tremors due to the earthquakes were felt in Jakarta, Bandung, and several parts of Java and Sumatra and more than 160,000 people were exposed and estimated release of energy to this earthquake (EQ) was 278 GWh. In this paper statistical analysis of the GPS-TEC data clearly supports the presence of earthquake signature in the form of anomalous perturbations in total electron content (TEC). Analysis found the presence of ionospheric perturbations 0–5 days before and after the main shock of the earthquake. The anomalous perturbations in the TEC were observed from few days to few hours prior to the main shock of the earthquake. Perturbations in TEC have been found to depend on the distance as well as direction of observation point from the epicentre. In general ionospheric perturbations after the EQ at all the stations are found larger than that before the EQ. VLF signal analysis using night-time fluctuation method indicates a significant increase in VLF amplitude before couple of days of EQ. Probable mechanisms behind these perturbations associated with EQ have also been discussed. © 2021, Akadémiai Kiadó.
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