GNSS-based communication systems, positioning accuracy, and space weather conditions are significantly influenced by Equatorial Plasma Bubbles (EPBs) and Traveling Ionospheric Disturbances (TIDs), especially in equatorial and low latitude regions such as India. The commonly used metric for tracing EPBs is the Rate of Total Electron Content Index (ROTI). Ground-based GNSS receivers are vital tools for detecting TIDs and EPBs by monitoring rapid variations in Total Electron Content (TEC). To accurately track irregularities, these receivers offer high-resolution temporal and spatial data in both quiet and geomagnetic conditions. In this study, the ionospheric disturbance index, namely the time-integrated ROTI (IROTI), is implemented to detect and classify both TIDs and EPBs, with a primary focus on its regional validation and application over the Indian sector. Seven geomagnetic storms which occurred on 17 March 2015, 23 April 2023, 10 May 2024, 8 September 2017, 23 June 2015, 19 April 2024, 11 October 2024 and eight quiet days on 21 May 2020, 7 July 2015, 15 September 2018, 28 January 2011, 1 January 2024, 10 April 2024, 12 June 2024, 25 October 2024 are counted for analysis using GNSS TEC data from Indian stations. IROTI Index on 17 March 2015 geomagnetic storm indicating both EPBs and TIDs with a higher spatial spread and clear temporal separation, with IROTI (EPB) values typically ranging from 8 to 40 TECU2 and IROTI (TID) values from 1.8 to 4.25 TECU2. The storm that occurred on 23 April 2023 exhibited IROTI (TID) activity between 0.64 and 3.1 TECU2 and IROTI (EPB) activity that typically ranged between 8 and 38.5 TECU2. During an extreme geomagnetic storm on 10 May 2024, IROTI values ranged between 8 and 60 TECU2 during EPBs. On 8 September 2017, a severe storm produced IROTI (TID) values between 0.3 and 2.12 TECU2 and IROTI (EPB) values ranging from 8 to 14 TECU2. The storm event observed on 23 June 2015 exhibited IROTI (TID) activity ranging from 0.2 to 4 TECU2. On 19 April 2024, a moderate geomagnetic storm, IROTI values were responsive between 8 and 40 TECU2 during EPBs, even on 11 October 2024, only EPBs were observed. Medium-scale TIDs (MSTIDs) were observed on eight quiet days mentioned above during post-sunset hours from 14:00–24:00 UT with magnitudes ranging from 0.2 to 2 TECU2. Statistical Analysis of ROTI and IROTI during TIDs periods is investigated for 7 geomagnetic storms and 8 quiet days, and a 92.3% detection efficiency for TIDs is found using IROTI, compared to only 7.69% using ROTI over the Indian region. The experimental findings demonstrate that IROTI performs noticeably better than conventional techniques such as ROTI across a range of geomagnetic conditions. The suggested index clearly distinguished between EPBs and TIDs and detected both. This approach offers a significant advancement for space weather monitoring and GNSS performance enhancement across equatorial and low-latitude regions.

A GNSS-based index IROTI analysis for distinguishability of TIDs and EPBs over low-latitude Indian region during geomagnetic storms

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发表日期：

2026年5月13日

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Srilatha Talluri,
M. Ravi Kumar,
Swapna Raghunath,
Devanaboyina Venkata Ratnam

摘要

GNSS-based communication systems, positioning accuracy, and space weather conditions are significantly influenced by Equatorial Plasma Bubbles (EPBs) and Traveling Ionospheric Disturbances (TIDs), especially in equatorial and low latitude regions such as India. The commonly used metric for tracing EPBs is the Rate of Total Electron Content Index (ROTI). Ground-based GNSS receivers are vital tools for detecting TIDs and EPBs by monitoring rapid variations in Total Electron Content (TEC). To accurately track irregularities, these receivers offer high-resolution temporal and spatial data in both quiet and geomagnetic conditions. In this study, the ionospheric disturbance index, namely the time-integrated ROTI (IROTI), is implemented to detect and classify both TIDs and EPBs, with a primary focus on its regional validation and application over the Indian sector. Seven geomagnetic storms which occurred on 17 March 2015, 23 April 2023, 10 May 2024, 8 September 2017, 23 June 2015, 19 April 2024, 11 October 2024 and eight quiet days on 21 May 2020, 7 July 2015, 15 September 2018, 28 January 2011, 1 January 2024, 10 April 2024, 12 June 2024, 25 October 2024 are counted for analysis using GNSS TEC data from Indian stations. IROTI Index on 17 March 2015 geomagnetic storm indicating both EPBs and TIDs with a higher spatial spread and clear temporal separation, with IROTI (EPB) values typically ranging from 8 to 40 TECU² and IROTI (TID) values from 1.8 to 4.25 TECU². The storm that occurred on 23 April 2023 exhibited IROTI (TID) activity between 0.64 and 3.1 TECU² and IROTI (EPB) activity that typically ranged between 8 and 38.5 TECU². During an extreme geomagnetic storm on 10 May 2024, IROTI values ranged between 8 and 60 TECU² during EPBs. On 8 September 2017, a severe storm produced IROTI (TID) values between 0.3 and 2.12 TECU² and IROTI (EPB) values ranging from 8 to 14 TECU². The storm event observed on 23 June 2015 exhibited IROTI (TID) activity ranging from 0.2 to 4 TECU². On 19 April 2024, a moderate geomagnetic storm, IROTI values were responsive between 8 and 40 TECU² during EPBs, even on 11 October 2024, only EPBs were observed. Medium-scale TIDs (MSTIDs) were observed on eight quiet days mentioned above during post-sunset hours from 14:00–24:00 UT with magnitudes ranging from 0.2 to 2 TECU². Statistical Analysis of ROTI and IROTI during TIDs periods is investigated for 7 geomagnetic storms and 8 quiet days, and a 92.3% detection efficiency for TIDs is found using IROTI, compared to only 7.69% using ROTI over the Indian region. The experimental findings demonstrate that IROTI performs noticeably better than conventional techniques such as ROTI across a range of geomagnetic conditions. The suggested index clearly distinguished between EPBs and TIDs and detected both. This approach offers a significant advancement for space weather monitoring and GNSS performance enhancement across equatorial and low-latitude regions.