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[MTT37-08] Impact of Ionospheric Disturbances on Global Navigation Satellite System Positioning During a Geomagnetic Storm in May 2024
In this study, we analyzed the ionospheric disturbances caused by a geomagnetic storm that occurred in May 2024 (minimum Dst index: -412 nT) and its impact on the positioning accuracy of the Global Navigation Satellite System (GNSS). For the analysis, we used GNSS observation data from GEONET (GNSS Earth Observation Network System) in Japan, and GEOSCI in Australia, to calculate positioning errors, total electron content (TEC), and the Rate Of TEC Index (ROTI).
We applied kinematic positioning to the GNSS data obtained from two GNSS receivers in Japan with an average mutual distance of approximately 30 km, and investigated the positioning errors across Japan during 8-11 May 2024. The average positioning errors on May 8–10 were 0.096 m, 0.089 m, and 0.118 m, respectively, whereas the average positioning error on May 11 increased to 0.458 m. Notably, the average positioning error between 19:00 and 20:00 UT on May 11 reached 1.428 m, marking a maximum increase of approximately 15 times compared to that on May 8–10. The daily-average ROTI at Toyota, Japan (35.4oN, 137.5oE) was 0.11 TECU/min on May 8, and 1.41 TECU/min on May 11. Maximum hourly-averaged TEC reached 2.16 TECU/min between 19:00 and 20:00 UT on May 11. Since this increase in ROTI is considered to be caused by electron density irregularities within plasma bubbles, the obtained result suggests that plasma bubbles reaching Japan led to the degradation of positioning accuracy.
A decrease in positioning accuracy was also observed in Australia, which is magnetically conjugate to Japan, on May 11, 2024. The average positioning error in Australia south of 30°S on May 11 was 2.226 m, and the one-hour average error between 15:00 and 16:00 UT reached 4.038 m.
During the period of significant positioning error increase on May 11, 2024, between 13:00 and 21:00 UT, the average absolute TEC was 27.2 TECU in Morioka, Japan, and 33.9 TECU in Cairns, Australia. Additionally, during the period of the largest recorded positioning error in Cairns (16:00–17:00 UT), the absolute TEC reached 50.8 TECU. Meanwhile, the average ROTI during the same period was 2.07 TECU/min in Morioka and 2.04 TECU/min in Cairns, showing no significant difference. Although temporal variation of ROTI is consistent with that of positioning errors, it was found that the magnitude of ROTI is not necessarily proportional to and that of positioning errors. In regions with high absolute TEC, even the same rate of variation results in a larger TEC fluctuation range, which increases the likelihood that the two GNSS receivers used for positioning will receive signals along paths with different TEC values, leading to greater positioning errors.
We applied kinematic positioning to the GNSS data obtained from two GNSS receivers in Japan with an average mutual distance of approximately 30 km, and investigated the positioning errors across Japan during 8-11 May 2024. The average positioning errors on May 8–10 were 0.096 m, 0.089 m, and 0.118 m, respectively, whereas the average positioning error on May 11 increased to 0.458 m. Notably, the average positioning error between 19:00 and 20:00 UT on May 11 reached 1.428 m, marking a maximum increase of approximately 15 times compared to that on May 8–10. The daily-average ROTI at Toyota, Japan (35.4oN, 137.5oE) was 0.11 TECU/min on May 8, and 1.41 TECU/min on May 11. Maximum hourly-averaged TEC reached 2.16 TECU/min between 19:00 and 20:00 UT on May 11. Since this increase in ROTI is considered to be caused by electron density irregularities within plasma bubbles, the obtained result suggests that plasma bubbles reaching Japan led to the degradation of positioning accuracy.
A decrease in positioning accuracy was also observed in Australia, which is magnetically conjugate to Japan, on May 11, 2024. The average positioning error in Australia south of 30°S on May 11 was 2.226 m, and the one-hour average error between 15:00 and 16:00 UT reached 4.038 m.
During the period of significant positioning error increase on May 11, 2024, between 13:00 and 21:00 UT, the average absolute TEC was 27.2 TECU in Morioka, Japan, and 33.9 TECU in Cairns, Australia. Additionally, during the period of the largest recorded positioning error in Cairns (16:00–17:00 UT), the absolute TEC reached 50.8 TECU. Meanwhile, the average ROTI during the same period was 2.07 TECU/min in Morioka and 2.04 TECU/min in Cairns, showing no significant difference. Although temporal variation of ROTI is consistent with that of positioning errors, it was found that the magnitude of ROTI is not necessarily proportional to and that of positioning errors. In regions with high absolute TEC, even the same rate of variation results in a larger TEC fluctuation range, which increases the likelihood that the two GNSS receivers used for positioning will receive signals along paths with different TEC values, leading to greater positioning errors.