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Deep learning-based prediction models for the vertical total electron content using GNSS satellite observations
(2026-08-01)
Mutasov, Gleb
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Myint, Lin Min Min
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Budtho, Jirapoom
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Perwitasari, Septi
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Nishioka, Michi
Ionospheric Total Electron Content (TEC) is a crucial parameter for characterizing the state of the ionosphere and assessing its impact on satellite-based navigation systems and on communication technologies. In equatorial and low-latitude regions, ionospheric irregularities, particularly equatorial plasma bubbles (EPBs), pose significant challenges for satellite navigation and communication due to their capacity to cause rapid TEC fluctuations and signal degradation. Since these effects are especially pronounced during ionospheric and geomagnetic disturbances, making accurate TEC prediction is an essential task for improving the reliability of GNSS-based positioning and space weather applications. This study presents a machine learning-based framework for one-day-ahead prediction of TEC with a 30-min resolution over the magnetic equator and low-latitude regions, with a focus on Southeast Asia. Unlike global models, our approach is tailored to local GNSS observations and directly predicts TEC values along specific satellite-receiver paths, defined by geographic location and satellite visibility. We integrate ionospheric pierce point (IPP) coordinates, geomagnetic indices, and solar activity indicators as features to enhance temporal and spatial forecasting accuracy. To address the nonlinear and nonstationary nature of TEC variations, we investigate and compare three deep learning architectures: a Transformer-based time-series model, a Temporal Kolmogorov–Arnold Network (TKAN), and a Long Short-Term Memory (LSTM). Additionally, the predictions are benchmarked against the empirical IRI-2020 model and a persistence baseline. The results demonstrate that both the Transformer and TKAN models outperform the LSTM and empirical approaches, particularly during different geomagnetic and ionospheric conditions, showing improved robustness and generalization. The proposed framework highlights the potential for accurate, resource-efficient TEC prediction in low-latitude regions and opens a pathway for further improvements by integrating multi-GNSS observations and additional space weather parameters.
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Improving One-Day-Ahead Forecasting of Low-Latitude Amplitude Scintillation Using an Upsampling-Enhanced LSTM
(2026-01-01)
Muangkammuen, Patinya
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Suthisopapan, Puripong
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Tongkasem, Napat
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Supnithi, Pornchai
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Kruesubthaworn, Anan
The scintillation in radio wave propagation, particularly in regions near the magnetic equator, is found to be introduced by the ionospheric irregularities causing unsatisfactory performance in satellite-based applications. In order to mitigate this effect, we design a long short-term memory (LSTM) model to forecast amplitude scintillation at 1-min resolution. In addition, the upsampling-based feature preprocessing is introduced to improve forecasting performance, especially for short-term severe scintillation events. In terms of R$^{2}$, which is a popular forecast evaluation metric, our proposed model exhibits about 20% improvement over the same LSTM model without upsampling. Furthermore, although existing studies achieve good forecasting accuracy up to 4 h ahead, the proposed model sets a benchmark with one-day-ahead forecasting, but at the cost of longer training time due to upsampling.
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Analysis of ionospheric and geomagnetic fields changes in Thailand during the May 2024 geomagnetic storm
(2025-12-15)
Myint, Lin M.M.
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Perwitasari, Septi
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Nishioka, Michi
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Saito, Susumu
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Kaewthongrach, Rungnapa
The extreme geomagnetic storm of May 2024, the most severe in two decades of space weather history up to date, had widespread effects on the ionosphere, from the polar regions to the magnetic equator. This study examines the responses of the equatorial ionosphere and geomagnetic field over Thailand during this geomagnetic storm, utilizing data from GNSS receivers, magnetometers, and ionosondes near the magnetic equator and low-latitude regions of Thailand. We analyze the direct and indirect impacts of interplanetary magnetic field (IMF) and interplanetary electric field (IEF) variations, driven by solar storms, on local equatorial magnetic fields and ionospheric parameters. Our finding reveals that storm-driven electric fields, particularly prompt penetration electric fields (PPEF) and disturbance dynamo electric fields (DDEF), strongly influenced equatorial electric field (EEF), causing notable fluctuations in total electron content (TEC), critical frequency of F2 (foF2), and virtual height of F layer (h’F). The Pearson correlation analysis highlights the rapid coupling between interplanetary magnetic field (IMF) and local equatorial magnetic fields during geomagnetic storms. These observations enhance our understanding of geomagnetic storm impacts in equatorial regions, which is crucial for improving space weather forecasting and mitigation strategies, especially for GNSS-dependent systems and radio communications.
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Thermosphere–Ionosphere Responses Over Thailand During the 2015 St. Patrick's Day Storm: Comparison of Observed O/N2 and VTEC With the SD WACCM-X Model Outputs
(2025-10-01)
Jamlongkul, Paparin
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Wannawichian, Suwicha
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Paxton, Larry J.
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Cantrall, Clayton E.
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Liu, Han Li
We present the first comparative analysis of observational data and model results focusing on thermospheric-ionospheric responses over the Thailand region by studying the St. Patrick's Day geomagnetic storm on 17–18 March, 2015. This study aims to advance our understanding of regional responses by building on previous observation-model comparisons. The observational data include global O/N<inf>2</inf> ratios from GUVI onboard the TIMED spacecraft, global vertical total electron content (VTEC) from the worldwide GNSS receivers obtained from the Madrigal database, and regional VTEC over Thailand from the KMI6 GNSS station. The atmospheric simulations used are from SD WACCM-X, incorporating high-latitude drivers from the Weimer and Assimilative Mapping of Ionospheric Electrodynamics (AMIE) models. The O/N<inf>2</inf> comparison focuses on TIMED's overpasses across Thailand at 3 UT (10 LT) on both days. Both models tend to reproduce general trends in the O/N<inf>2</inf> ratio and VTEC variations prior to the storm onset. The SD WACCM-X/Weimer model shows better agreement with the O/N<inf>2</inf> ratio from GUVI observations over Thailand, particularly during the recovery phase. Meanwhile, the SD WACCM-X/AMIE model better captures VTEC trends on both large and localized scales, especially after sunset, and successfully reproduces localized features over Thailand. However, during the early recovery phase, both Weimer and AMIE drivers fail to fully capture the collapse of the equatorial ionospheric anomaly (EIA) as indicated by VTEC data, likely due to overestimated (Formula presented.) drift values at low latitudes.
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Corrigendum to “Spatio-temporal characteristics of ionospheric irregularities in low latitude regions during the peak of solar cycle 25” [Adv. Space Res. 76(1) (2025) 254–268, (S0273117725004168), (10.1016/j.asr.2025.04.062)]
(2025-09-01)
Tongkasem, Napat
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Supnithi, Pornchai
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Thammavongsy, Phimmasone
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Nishioka, Michi
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Perwitasari, Septi
The authors regret that the following was omitted from the acknowledgment section: This research project is also financially supported by National Research Council of Thailand (NRCT) under grant N41A640235. The authors would like to apologise for any inconvenience caused.
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Spatio-temporal characteristics of ionospheric irregularities in low latitude regions during the peak of solar cycle 25
(2025-07-01)
Tongkasem, Napat
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Supnithi, Pornchai
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Thammavongsy, Phimmasone
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Nishioka, Michi
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Perwitasari, Septi
Equatorial plasma bubbles (EPBs) are a primary source of ionospheric irregularities (IIR) in low-latitude regions. The severity of EPBs depends on the intensity, penetration, and disturbance of electric fields generated in the ionosphere. In this work, we analyze the IIR associated with geomagnetic activity in the low-latitude region (0°N–25°N, 90°E–110°E) from 2022 to 2024. The total electron content (TEC) and the rate of TEC index (ROTI) are used to investigate the spatiotemporal characteristics of these IIRs, influenced by both local EPBs and global geomagnetic storms. During low-to-moderate geomagnetic activity, electric field penetration and disturbances have a low impact on EPB development. The high solar activity intensifies the electric field, leading to intense EPB occurrences that can affect the entire region for several hours. From January 2022 to October 2024, these intense EPB events accounted for 35% of all EPB occurrences. During strong geomagnetic storms, the prompt penetration of electric fields (PPEF), and disturbance dynamo electric field (DDEF) caused the depression and fluctuations of TECs.
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Sporadic E critical frequency detection using three EIA region ionosonde stations over Southeast Asia
(2025-03-01)
Wichaipanich, Noraset
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Nishioka, Michi
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Min Myint, Lin Min
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Supnithi, Pornchai
This paper presents the occurrence of the sporadic E layer critical frequency (foEs) measured from three ionosonde stations in the Southeast Asia equatorial ionization anomaly (EIA) regions. These three ionosonde stations include two in Thailand: Chiang Mai (18.76°N, 98.93°E, Dip 12.7°) and Chumphon (10.72°N, 99.37°E, Dip 3.0°), and one in Indonesia: Kototabang (0.2°S, 100.32°E, Dip −10.1°). The daily hourly foEs values observed during 2010 and 2015 were statistically analyzed for foEs occurrence during low and high solar activity periods. Additionally, the number of foEs occurrences was analyzed in terms of the percentage of occurrence (%foEs). The results show that the occurrences of foEs from all three stations were similar, with the monthly hourly occurrence of foEs peaking in the June solstice season (May, June, July, August). Meanwhile, foEs appeared relatively low during the September equinox (September, October) and the December solstice (November, December, January, February) seasons. Furthermore, the frequency of foEs occurrence peaks around 16–20 LT, except in 2015 at Chiang Mai and Chumphon, where peaks were observed at 10 LT and 15 LT, respectively. Additionally, comparing the three stations reveals that in 2010, the maximum number of foEs occurrences was at Chiang Mai (≈21 %), followed by Kototabang (≈19 %) and Chumphon (≈16 %). In 2015, the highest number was observed at Kototabang (≈17 %), followed by Chumphon (≈14 %) and Chiang Mai (≈8%). Furthermore, the maximum frequency of foEs was highest at Chiang Mai (20–25 MHz), followed by Chumphon (15–20 MHz) and Kototabang (10–15 MHz). Additionally, foEs occurrences during low solar activity (2010) were higher than those during high solar activity (2015). It was assumed that the occurrence of foEs in the Southeast Asian sector was anti-correlated with the solar cycle and asymmetric characteristics. We hope that this analytical information will be useful for future HF and VHF communications design in the Southeast Asia region.
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A Combination Approach for 2-D Interference Channel Based on Factor Graph in BPMR System
(2025-02-01)
Sopon, Thanomsak
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Supnithi, Pornchai
High areal density in bit-patterned media recording (BPMR) systems encounters several challenges, such as two-dimensional (2-D) interference channels and media noises in the presence of severe fluctuations. To combat the effects of the 2-D interference channel, a factor graph-based detector (FGB) is one of the promising detectors for the 2-D detection that can mitigate the channel impairment. In this paper, we propose an improvement of factor graph decoding for 2-D interference channels of the BPMR system. The 2-D interference channel is separated into the two targets that are the upper triangular target and the lower triangular target. After that, the joint outputs are averaged for each detector. The simulation results show that the proposed FGB detector method achieves lower bit error rate (BER) performances than both the conventional FGB detector and the 2-D FGB detector on the BPMR system with an areal density of 3 and 4 Tb/in<sup>2</sup>.
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Impact of ionospheric disturbances on NIC and NACp degradation in ADS-B messages
(2025-01-01)
Takahashi, Toru
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Pongpeaw, Anurak
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Saito, Susumu
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Koga, Tadashi
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Supnithi, Pornchai
Southern Japan is located in the low geomagnetic latitude region, where amplitude scintillations associated with equatorial plasma bubbles are often observed. The Electronic Navigation Research Institute (ENRI) has installed GNSS scintillation receivers and an all-sky camera on Ishigaki Island to monitor ionospheric disturbances. The GNSS receivers used are Septentrio Pola5S, which are also utilized for the Ground Based Augmentation System (GBAS) at New Ishigaki Airport (24.4 deg. N, 124.2 deg. E), which is the southernmost airport with regular flights in Japan. The all-sky camera can capture ionospheric disturbances, such as plasma bubbles. The ADS-B receiver has also been installed at Ishigaki Island and received its message within almost 150 NM. The ADS-B observation on Ishigaki Island has been operational since 2023. We observed that plasma bubbles and degradations in NIC and NACp values occurred simultaneously on March 16, 2024. We calculated the Ionospheric Pierce Points (IPP) of GPS satellites observed by aircraft showing degraded NIC and NACp values. Plasma bubbles captured by the all-sky camera were projected onto the map. One GPS satellite's IPP from the flight, which sent those degraded values, was located at the edge of a plasma bubble, and the potential impact of the plasma bubble was considered. However, same analyses were conducted on two other satellites flying in the vicinity, and although these two flights were in conditions that were either equivalent to or more susceptible to the effects of the plasma bubble, neither the NIC nor NACp showed any degradation. Therefore, Instead, radio frequency interference (RFI), or equipment failure is likely one of the causes of these degradations.
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Global landscape of space weather observations, research and operations
(2025-01-01)
Ishii, Mamoru
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Costa, Joaquim E.R.
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Kuznetsova, Maria
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Bisi, Mario M.
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Meza, Amalia
The recognition of space weather hazards is increasingly growing, highlighting the importance of monitoring and forecasting it. High precision satellite positioning techniques have become essential in various areas of social and economic infrastructure. However, it is well-known that Global Navigation Satellite Systems (GNSS) can be affected by space weather-induced ionospheric variations. This poses a challenge as it can impact the reliability and accuracy of GNSS-based systems. Space weather phenomena can also have significant effects on aviation systems and electric power grids. Given that many of these phenomena occur on a global scale, it is crucial to have a comprehensive monitoring and observation network. Currently, numerous ground-based observations are managed by local government or academic bodies. In contrast, space-based observations are typically operated by space agencies, often necessitating international coordinated collaboration to undertake significant projects in this field. The paper puts a strong emphasis on the need for collaboration between various entities in each nation and between national programmes. In this paper, the authors provide an overview of the international landscape for space weather research and operations at the nation-state level. They also highlight the activities of various national and regional space agencies involved in space weather research and monitoring for enhancing our capabilities in monitoring, forecasting, and mitigating the impacts of space weather phenomena on critical infrastructure and systems.

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