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Abstract <p>Utilizing the advantage of the almost stable NavIC (Navigation with Indian constellation) satellite links over the Indian region, this study, for the first time, reports latitudinal and seasonal variations in the NavIC total electron content (TEC) across the Indian region during the lowest solar activity period of the year 2020. Characteristics of the observed TEC are notably obtained from a NavIC satellite (stationed at 83°E longitude) using the dual frequency transmission in the S-band (2492.028&#xa0;MHz) and L5-band (1176.45&#xa0;MHz). Significantly, the measurements are collected from the NavIC receivers placed at six sites located at different latitudes along a longitude of ~77°E thus covering the latitudinal Indian region from geodetic latitude 8°N up to 32°N (geomagnetic latitude ~0°N up to ~24°N). Major findings from this study show a strong winter and equinoctial anomaly, which are found to switch their character when the stations are either dip-equatorward or poleward from the crest location of the equatorial ionization anomaly (EIA). Another significant result elucidates the night-time VTEC enhancement as well as large night-to-night background variability, which is mainly observed during the summer months of 2020. Further, this study cross-examines the morphology of the ionosphere over the Indian region using a stable link from the NavIC satellite and presents a lucid comparison of results with the Vertical TEC (VTEC) estimated using the standard International Reference Ionosphere (IRI)-2016 model. Most of the morphological characters of VTEC variations are found in conformity with previous studies, with a few significant latitudinal changes noted above. However, even during the lowest solar activity, large differences are found between the observed and IRI-model VTEC values, which show an unusually strong seasonal and latitudinal dependence and stress for further needful investigation, both in the modelling and the observation domains.</p> Research highlights <p>With the advent of India’s own satellite navigation system, known as NavIC, a new opportunity for ionospheric observations with a very stable satellite link is created. This study, for the first time, gives a detailed account of continuous and highly accurate TEC (total electron content) observations from the high-elevation link using a ground chain of 6 NavIC receiver stations along the longitude of ~77°E. A comprehensive analysis focused on resolving different patterns in TEC variability has revealed that the present understanding of the equinoctial asymmetry, winter anomaly and the summer night-time TEC enhancements compared to the nocturnal background TEC of other seasons falls short to explain newly found features. The contrasting latitudinal changes between the dip-equator and the crest of the anomaly versus those beyond the crest latitudes in the context of anomalous variations are discussed and explained to the extent possible in light of the existing literature on these features.</p>

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Characteristics of NavIC based total electron content over Indian region and comparison with IRI-2016 model

  • 期刊论文

  • 发表日期：

    2025年8月20日

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  • Anu Arora,
  • Nirvikar Dashora,
  • Sharda Vashisth,
  • Amitava Sen Gupta

摘要

Abstract

Utilizing the advantage of the almost stable NavIC (Navigation with Indian constellation) satellite links over the Indian region, this study, for the first time, reports latitudinal and seasonal variations in the NavIC total electron content (TEC) across the Indian region during the lowest solar activity period of the year 2020. Characteristics of the observed TEC are notably obtained from a NavIC satellite (stationed at 83°E longitude) using the dual frequency transmission in the S-band (2492.028 MHz) and L5-band (1176.45 MHz). Significantly, the measurements are collected from the NavIC receivers placed at six sites located at different latitudes along a longitude of ~77°E thus covering the latitudinal Indian region from geodetic latitude 8°N up to 32°N (geomagnetic latitude ~0°N up to ~24°N). Major findings from this study show a strong winter and equinoctial anomaly, which are found to switch their character when the stations are either dip-equatorward or poleward from the crest location of the equatorial ionization anomaly (EIA). Another significant result elucidates the night-time VTEC enhancement as well as large night-to-night background variability, which is mainly observed during the summer months of 2020. Further, this study cross-examines the morphology of the ionosphere over the Indian region using a stable link from the NavIC satellite and presents a lucid comparison of results with the Vertical TEC (VTEC) estimated using the standard International Reference Ionosphere (IRI)-2016 model. Most of the morphological characters of VTEC variations are found in conformity with previous studies, with a few significant latitudinal changes noted above. However, even during the lowest solar activity, large differences are found between the observed and IRI-model VTEC values, which show an unusually strong seasonal and latitudinal dependence and stress for further needful investigation, both in the modelling and the observation domains.

Research highlights

With the advent of India’s own satellite navigation system, known as NavIC, a new opportunity for ionospheric observations with a very stable satellite link is created. This study, for the first time, gives a detailed account of continuous and highly accurate TEC (total electron content) observations from the high-elevation link using a ground chain of 6 NavIC receiver stations along the longitude of ~77°E. A comprehensive analysis focused on resolving different patterns in TEC variability has revealed that the present understanding of the equinoctial asymmetry, winter anomaly and the summer night-time TEC enhancements compared to the nocturnal background TEC of other seasons falls short to explain newly found features. The contrasting latitudinal changes between the dip-equator and the crest of the anomaly versus those beyond the crest latitudes in the context of anomalous variations are discussed and explained to the extent possible in light of the existing literature on these features.