KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 10

Some of the metrics are blocked by your
consent settings
Analysis of ionospheric and geomagnetic fields changes in Thailand during the May 2024 geomagnetic storm
(2025-12-15)
Myint, Lin M.M.
;
Perwitasari, Septi
;
Nishioka, Michi
;
Saito, Susumu
;
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.
Some of the metrics are blocked by your
consent settings
Spatio-temporal characteristics of ionospheric irregularities in low latitude regions during the peak of solar cycle 25
(2025-07-01)
Tongkasem, Napat
;
Supnithi, Pornchai
;
Thammavongsy, Phimmasone
;
Nishioka, Michi
;
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.
Some of the metrics are blocked by your
consent settings
Compatibility of Low-Cost GNSS Receivers for Total Electron Content (TEC) Analysis
(2025-01-01)
Rana, Bhim Bahadur
;
Supnithi, Pornchai
;
Myint, Lin M.M.
;
Tongkasem, Napat
;
Budtho, Jirapoom
Although the geodetic GNSS receivers are highly precise, they are inaccessible to every user, especially in remote areas. Therefore, this work aimed to find the reasons that bolster the low-cost GNSS receivers to be used with high resolution over a wide area, instead of geodetic in space weather studies. A comparative analysis was conducted between a low-cost Ublox ZED-F9P GNSS receiver and a geodetic Novatel Propak6 GNSS receiver, focusing on ionospheric parameters such as slant total electron content (STEC), vertical total electron content (VTEC), and the number of satellites tracked using the Global Positioning System (GPS). Additionally, VTEC values were compared with the GIM model. Both receivers exhibited a similar pattern of TEC, with the R2 value of 0.9734 and the root mean square error of 3.4583. The number of satellites tracked by both receivers during the observed periods was also found to be similar. Moreover, the VTEC results obtained from the low-cost GNSS receiver showed compatibility with the GIM model, demonstrating the reliability of the low-cost receiver in comparison to the geodetic GNSS receiver.
Some of the metrics are blocked by your
consent settings
Study on Effect of Equatorial Plasma Bubble over Real-Time Kinematic Positioning in Bangkok Thailand
(2022-01-01)
Thu, Phyo C.
;
Supnithi, Pornchai
;
Myint, Lin Min Min
;
Budtho, Jirapoom
;
Saito, Susumu
Equatorial plasma bubbles (EPBs) depict local ionospheric irregularity in low-latitude regions which can spread to mid-latitude regions. In this work, we analyzed the effects of the EPBs on the performance of real-time kinematic (RTK) positioning at the short, medium, and long baselines in Bangkok, Thailand. We used the kinematic positioning mode provided by a free and open-source software (FOSS) package called RTKLIB to analyze the positioning errors. It is found that the positioning errors are higher during the disturbance periods and more severe in the long baseline case.
Some of the metrics are blocked by your
consent settings
A Preliminary Neural Network Model for Range Spread-F Events at Chumphon Station, Thailand
(2018-12-24)
Thammavongsy, Phimmasone
;
Phakphisut, Watid
;
Supnithi, Pornchai
In this work, we develop a preliminary neural network model for range-Type spread-F events over Chumphon station (10.7N latitude, 99.4E longitude), Thailand. The spread-F neural network model is designed with the input parameters including seasonal variations, diurnal variations, window-Averaged magnetic activity (Ap index) and window-Averaged solar activity (F10.7 index). The model is based on the ionogram data during the 24 <sup>th</sup> solar cycle from 2013 to 2016. As a result, the proposed model can provide the predicted results and the network performance of 97.8% for correct classification.
Some of the metrics are blocked by your
consent settings
Total electron content observations by dense regional and worldwide international networks of GNSS
(2018-06-01)
Tsugawa, Takuya
;
Nishioka, Michi
;
Ishii, Mamoru
;
Hozumi, Kornyanat
;
Saito, Susumu
Two-dimensional ionospheric total electron content (TEC) maps have been derived from ground-based Global Navigation Satellite System (GNSS) receiver networks and applied to studies of various ionospheric disturbances since the mid-1990s. For the purpose of monitoring and researching ionospheric conditions and ionospheric space weather phenomena, we have developed TEC maps of areas over Japan using the dense GNSS network, GNSS Earth Observation NETwork (GEONET), which consists of about 1300 stations and is operated by the Geospatial Information Authority of Japan (GSI). Currently, we are providing high-resolution, two-dimensional maps of absolute TEC, detrended TEC, rate of TEC change index (ROTI), and loss-of-lock on GPS signal over Japan on a real-time basis. Such high-resolution TEC maps using dense GNSS receiver networks are one of the most effective ways to observe, on a scale of several 100 km to 1000 km, ionospheric variations caused by traveling ionospheric disturbances and/or equatorial plasma bubbles, which can degrade single-frequency and differential GNSS positioning/navigation. We have collected all the available GNSS receiver data in the world to expand the TEC observation area. Currently, however, dense GNSS receiver networks are available in only limited areas, such as Japan, North America, and Europe. To expand the two-dimensional TEC observation with high resolution, we have conducted the Dense Regional and Worldwide International GNSS TEC observation (DRAWING-TEC) project, which is engaged in three activities: (1) standardizing GNSS-TEC data, (2) developing a new high-resolution TEC mapping technique, and (3) sharing the standardized TEC data or the information of GNSS receiver network. We have developed a new standardized TEC format, GNSS-TEC EXchange (GTEX), which is included in the Formatted Tables of ITU-R SG 3 Data-banks related to Recommendation ITU-R P.311. Sharing the GTEX TEC data would be easier than sharing the GPS/GNSS data among those in the international ionospheric researcher community. The DRAWING-TEC project would promote studies of medium-scale ionospheric variations and their effect on GNSS.
Some of the metrics are blocked by your
consent settings
Nominal ionospheric delay gradient estimation at Suvarnabhumi airport, Thailand
(2017-10-19)
Budtho, Jirapoom
;
Supnithi, Pornchai
;
Saekow, Apitep
;
Saito, Susumu
Ground-Based Augmentation System (GBAS) allows high-precision aircraft landing based on Global Navigation Satellite System (GNSS) at large airports. However, non-uniform spatial ionospheric delay needs to be determined. In this work, we compute the nominal ionospheric delay gradients around Suvarnabhumi airport, Thailand. The utilized techniques involve Kalman filter and LAMBDA method. Based on the measurements on DOY 043 of 2015, we found that the ionospheric delay gradients are less than 20 mm/km. With the improved ambiguity ratio test to obtain higher success rate than previous works, the standard deviation σ<inf>VIC</inf> is 5.27 mm/km.
Some of the metrics are blocked by your
consent settings
Ionospheric peak height at the magnetic equator: Comparison between ionosonde measurements and IRI
(2017-07-15)
Maruyama, Takashi
;
Ma, Guanyi
;
Tsugawa, Takuya
;
Supnithi, Pornchai
;
Komolmis, Tharadol
The ionospheric peak height in the F layer (hmF2) varies with not only thermospheric conditions but also dynamic processes in the upper atmosphere. At mid-latitudes, the field-aligned diffusion and recombination loss determine the hmF2 in the absence of applied vertical drift. Vertical drifts displace the hmF2 to a new equilibrium position in conjunction with the field-aligned redistribution of the plasma. In the vicinity of the magnetic equator, however, the equilibrium state would be different from low and mid-latitudes because the direct vertical coupling of plasma through the diffusion process is not allowed. Thus the behavior of hmF2 cannot be simply an extrapolation of that at low latitudes. In this paper, ionosonde measurements of the hmF2 near the magnetic equator and off-equatorial latitudes are compared with the IRI output.
Some of the metrics are blocked by your
consent settings
Statistical Analysis of Separation Distance between Equatorial Plasma Bubbles
(2017-05-17)
Bumrungkit, Acharaporn
;
Supnithi, Pornchai
Equatorial plasma bubbles in the low-latitude regions can cause loss-of-lock resulting to the availability of ground-based augmentation system (GBAS) due to increased ionospheric gradients. For realistic simulation, distances between adjacent bubbles need to be determined. In this study, we analyze the statistics of this parameter around the Suvarnabhumi international airport, Thailand. This work presents the methodology to estimate the separation distance between visible plasma bubbles on the same day. To detect the equatorial plasma bubbles, we analyze the slant total electron content (STEC), which is obtained from the dual-frequency GNSS receiver located at King Mongkut's Institute of Technology Ladkrabang (geographic, 13.7278o N, 100.7726o E). The results show that the separation distance between plasma bubbles on anomalous ionosphere are in range of 30 to 150 kilometers.
Some of the metrics are blocked by your
consent settings
Loss-of-lock statistics from the GPS receiver near Suvarnabhumi airport, Thailand
(2011-10-03)
Le Hoai, Phong Pham
;
Rungraengwajiake, Sarawoot
;
Supnithi, Pornchai
Loss-of-lock (LOL) statistics are important to the study of the ionosphere and the availability of the GPS/GNSS technology. The LOL data of the GPS, for instance, together with the spread-F and the rate of TEC change index (ROTI) are often used to the study of plasma bubble occurrence in the low and equatorial latitudes. In our work, we collected the data from the GPS receiver near Suvarnabhumi airport, Thailand, in 2010 and investigated the LOL statistics during this time. The number of proposed parameters including the probability of visible GPS satellites with LOL, and the number of usable GPS satellites are used to evaluate the LOL statistics. A comparison of the probability of LOL on both GPS frequency carriers indicates that the L<inf>2</inf> frequency is more susceptible to the LOL events than L<inf>1</inf> frequency. The results also show that the dense LOL occurrence is related to high fluctuation ROTI. The inversely correlation between elevation angles and number of visible GPS satellites with LOL is obtained as well. © 2011 IEEE.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results