Kenpankho, Prasert

Preferred name

Kenpankho, Prasert

Alternative Name

Kenpankho, P.

Main Affiliation

School of Industrial Education and Technology

prasert.ke@kmitl.ac.th

Now showing 1 - 9 of 9

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Variation of ionospheric slab thickness observations at Chumphon equatorial magnetic location
(2011-01-01)
Kenpankho, P.
;
Supnithi, P.
;
Tsugawa, T.
;
Maruyama, T.
This study presents the diurnal and seasonal variations of slab thickness at the equatorial magnetic latitudes in Thailand during 2004-2006, corresponding to the declining part of low solar activity. The GPS-derived total electron content (TEC) and the maximum electron density of the F-region (N <inf>m</inf>F<inf>2</inf>) are used to compute the slab thickness (&tau) at the Chumphon station (10.72°N, 99.37°E), located near the magnetic equator. The results show that large peaks of slab thickness exist during the pre-sunrise hours in all three seasons at Chumphon when compared with other latitudes. The maximum value of slab thickness occurs when the peak electron density in the F<inf>2</inf> region is at the lowest level. During daytime, the slab thickness ranges from 200 kilometers to 580 kilometers for all seasons. During nighttime, the maximum value of slab thickness is 1250 kilometers in the summer of 2004. Moreover, the diurnal variation shows two minima that appear around 0900 LT and 1900 LT, during the post-sunrise and sunset hours. The seasonal variations show that the average slab thickness daily value is greater during summer and winter than those during equinox. Our study finds that the slab thickness at Chumphon located near the equatorial latitude is much larger than those found at low, mid, and high latitudes. The difference in slab thickness between the equatorial latitude and other zones is explained by the lack of plasma flow from the plasmasphere to the F<inf>2</inf> region at the magnetic equator. Copyright © The Society of Geomagnetism and Earth.
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Estimation of the single GPS-receiver bias using the gradient descent algorithm
(2016-09-06)
Chiablaem, Athiwat
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Supnithi, Pornchai
;
Klinngam, Somjai
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Panachart, Chaiwat
;
Saekow, Apithep
The ionospheric Total Electron Content (TEC) can be obtained from processing measurements of the dual-frequency Global Positioning System (GPS) receiver. The main sources of errors in the TEC calculation are satellite and receiver biases. In this paper, we apply the gradient descent algorithm on the receiver bias estimation. The TEC is derived from measurements at 12 dual-frequency GPS stations in Thailand. The criterion of receiver bias estimation is based on the minimum sum of the vertical TEC (VTEC) standard deviation method. The results show that the maximum receiver bias value is approximately 3.69 ns at UDON station, while the minimum value is -5.91 ns at SRTN station. The accuracy of the receiver biases from this algorithm is compared with the reference method. The maximum percentage deviation is about 7.5% at SRTN station. The percentage deviation of the minimum sum of the VTEC between the reference method and the proposed method from all stations are less than 0.05%. Thus, the proposed algorithm is a viable option to estimate the receiver bias.
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Ionospheric disturbances as precursor signals of the March 28, 2025, Myanmar earthquake
(2026-03-15)
Pansong, C.
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Ruttanaburee, S.
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Pornsopin, P.
;
Kenpankho, P.
This study examined the ionospheric response associated with the Mw 7.7 Myanmar earthquake on March 28, 2025, using GPS-derived Total Electron Content (TEC) data from seven GNSS stations across Thailand. TEC variations were analyzed alongside Dst and Kp indices, as well as ionosonde-derived parameters, namely the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), the disturbances in NmF2, and the slab thickness (τ), which were obtained from three IGS-supported stations. We detected abnormal variations in TEC approximately 15 days before the earthquake (13–27 March 2025), characterized by alternating positive and negative deviations. The TEC exhibited alternating positive and negative deviations throughout the analysis period, reflecting ionospheric variability prior to the earthquake. During the early period (13–18 March), the deviations remained within approximately ±6 TECU. However, from 19 to 21 and 23–24 March, moderate fluctuations were observed, particularly at mid- and low-latitude stations (UTHG, THBK, THCP, and THPK), where ΔTEC ranged from ±6 to 10 TECU. The TEC decrease occurred on 25 March under weak geomagnetic conditions (Dst > −30 nT) at the northern stations MAEH (−18.40 TECU), THCM (−15.65 TECU), and NANN (−15.73 TECU), marking the most pronounced negative anomaly observed during the study period. Subsequently, on 26–27 March, TEC values recovered to positive anomalies of +4 to +10 TECU, indicating a return to normal ionospheric conditions. To objectively identify pre-seismic ionospheric anomalies, a Median Absolute Deviation (MAD) approach was applied using a ±1.34MAD threshold. This statistical technique effectively detects subtle deviations while minimizing transient noise. The results reveal coherent TEC depletions across multiple stations on 25 March, suggesting the presence of localized ionospheric disturbances potentially related to seismo-ionospheric processes rather than geomagnetic effects. Furthermore, concurrent anomalous increases in foF2 and hmF2, along with a reduction in slab thickness near the epicentral region, indicate vertical uplift of the F2 layer, consistent with possible Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanisms.
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GNSS Receiver Bias Model for Near Real Time TEC Monitoring at Low Latitude, Thailand
(2026-01-01)
Kenpankho, Prasert
;
Maichuen, Samatchaya
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Phothila, Prarinya
;
Zhang, Jianfeng
;
Keokhumcheng, Thanapon
This research proposes and investigates GNSS receiver bias modeling for near real time total electron content (TEC) monitoring across 16 multi-frequency GNSS stations in low latitude, Thailand, from 2022-2024. By applying a refined methodology based on Kenpankho et al. (2021) and integrating IONOLAB-BIAS for single station bias estimation, the research corrects for satellite and receiver inter-frequency biases to enhance TEC accuracy. Results show a consistent upward trend in TEC values, reflecting increased latitudes, seasonal ionospheric activity, and geomagnetic storms. Comparative analysis with the IRI 2020 model using correlation coefficients and RMSE reveals spatial and temporal variation, with near equatorial latitude stations showing strong alignment than upper low latitude stations. The results highlight the importance of localized GNSS-based TEC models for improving satellite positioning accuracy in equatorial regions and highlight the limitations of global models under dynamic ionospheric conditions.
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Comparison of observed TEC values with IRI-2007 TEC and IRI-2007 TEC with optional foF2 measurements predictions at an equatorial region, Chumphon, Thailand
(2013-11-15)
Kenpankho, P.
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Supnithi, P.
;
Nagatsuma, T.
In this research, as part of working towards improving the IRI over equatorial region, the total electron content (TEC) derived from GPS measurements and IRI-2007 TEC predictions at Chumphon station (10.72 N, 99.37 E), Thailand, during 2004-2006 is analyzed. The seasonal variation of the IRI-2007 TEC predictions is compared with the TEC from the IRI-2007 TEC model with the option of the actual F2 plasma frequency (foF2) measurements as well as the TEC from the GPS and International GNSS service (IGS). The Chumphon station is located at the equatorial region and the low latitude of 3.22 N. For a declining phase of the solar cycle (2004-2006), the study shows that the IRI-2007 TEC underestimates the IRI-2007 TEC with the foF2 observation at the nighttime by about 5 TECU. The maximum differences are about 15 TECU during daytime and 5 TECU during nighttime. The overestimation is more evident at daytime than at nighttime. When compared in terms of the root-mean square error (RMSE), we find that the highest RMSE between GPS TEC and IRI 2007 TEC is 14.840 TECU at 1230 LT in 2004 and the lowest average between them is 1.318 TECU at 0630 LT in 2006. The noon bite-out phenomena are clearly seen in the IRI-2007 TEC with and without optional foF2 measurements, but not on the GPS TEC and IGS TEC. The IRI TEC with optional foF2 measurements gives the lowest RMSE values between IRI TEC predicted and TEC measurement. However, the TEC measurements (GPS TEC and IGS TEC) are more correct to use at Chumphon station. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.
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Low latitude TEC disturbances during extreme geomagnetic storms: insights into March and May 2024
(2025-12-15)
Pansong, C.
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Wongsak, P.
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Ruttanaburee, S.
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Pornsopin, P.
;
Kenpankho, P.
This study investigates the variations of the Total Electron Content (TEC) in response to the extreme geomagnetic storms at the low latitudes over Thailand in 2024. For analyzing data from geomagnetic storms recorded in March and May 2024, with Dst maximum to −412 nT and Kp index to 9 on May 11, 2024, Dst at −351 nT and Kp at 9- on May 10, 2024, Dst at −159 nT and Kp at 7 on May 12, 2024, and Dst at −128 nT and Kp at 8 + on March 24, 2024. This study conducted a 13-day analysis for maximum negative Dst storm event, encompassing six days before and six days after the event. Data were sourced from GNSS receiver stations at Chiang Mai (THCM: 19.21°N, 99.12°E, 9.96°N Dip), Bangkok (THBK: 13.73°N, 100.78°E, 4.82°N Dip), and Chumphon (THCP: 10.72°N, 99.38°E, 1.85°N Dip), Thailand. The study highlights a significant TEC disturbance that increases during the extreme geomagnetic storm, particularly at THCP, next to equatorial latitude. TEC increases at a heightened sensitivity to geomagnetic storms. As a result, TEC reached up to 60 TECU from the average TEC of the six previous days and six posterior days excluding the maximum storm event day at a low latitude. The intense nighttime geomagnetic storms were a few events that resulted in minimal TEC gap increases compared to the daytime geomagnetic storms. Additionally, the correlation coefficient between geomagnetic storm levels and TEC disturbances is strongly and significantly linked to storm intensity. The signature of TEC disturbance is influenced during extreme geomagnetic storms in the ascending phase of Solar Cycle 25 at low latitudes, emphasizing the importance of enhanced understanding of TEC behavior in low latitude regions.
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Low-Latitude Ionospheric Responses to Two Matched Intense Equinoctial Geomagnetic Storms: A Case-Based Comparison Between Solar Cycles 24 and 25
(2026-01-16)
Pansong, Chollada
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Kenpankho, Prasert
This study investigates the ionospheric responses to two matched intense equinoctial geomagnetic storms that occurred during Solar Cycles 24 and 25 (SCs 24 and 25), with emphasis on variations in Total Electron Content (TEC), the F2-layer critical frequency (foF2), and the F2-layer peak height (hmF2). TEC data were derived from Global Ionospheric Maps (GIMs) based on Global Navigation Satellite System (GNSS) observations, while foF2 and hmF2 parameters were obtained from the Global Assimilative Model of the Bottomside Ionosphere Timeline (GAMBIT) for 22 low-latitude locations worldwide. The results show that the SC25 storm produced stronger and more spatially extensive ionospheric responses than the SC24 event. Peak TEC values during SC25 exceeded those of SC24 by up to ~80-90 TECU in the Southeast Asian, East Asian, and Pacific sectors near the storm main phase, indicating a pronounced positive ionospheric storm. These enhancements are closely associated with higher solar wind speeds (~650-700 km s–1) and strongly fluctuating IMF Bz during SC25, which generated sustained multi-pulse Prompt Penetration Electric Fields (PPEFs) that intensified E × B plasma drifts and the equatorial fountain effect. In contrast, SC24 was characterized by lower solar wind speeds (~550-600 km s–1) and a predominantly southward IMF Bz, resulting in shorter-lived PPEF activity, weaker TEC enhancements, and pronounced depletion during the recovery phase. Correlation analysis between Dst and TEC disturbances reveals strong negative correlations (r ≈ −0.6 to −0.9) in the Asia-Pacific sectors during the main phase, indicating that enhanced TEC disturbances tend to coincide with periods of increasing storm intensity, whereas predominantly positive correlations (r ≈ 0.6-0.9) are observed in the Middle Eastern-African-European sector, reflecting TEC depletion. The foF2 response shows clear phase dependence, with localized daytime enhancements during the main phase but widespread reductions of ~15-20% during recovery in both solar cycles, consistent with the influence of Disturbance Dynamo Electric Fields (DDEFs), and thermospheric composition changes. In contrast, hmF2 exhibits solar-cycle-dependent behavior, with modest increases (~3-8%) during SC24 and more variable, often negative responses (up to ~2-3% decrease) during SC25. These findings highlight the heterogeneous, region-dependent, and solar cycle-dependent nature of ionospheric variability during intense geomagnetic storms, with important implications for space weather modeling and prediction.
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The study on the relationship between ionospheric delay and low-cost localizing robots
(2025-03-01)
Sumniang, Patiphan
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Sittichai, Wishapol
;
Kenpankho, Prasert
The dispersive and anisotropic nature of the ionosphere above certain regions particularly on Thailand's low − nearly equatorial − latitude, positioning accuracy is seriously affected when using a precision limited model. Change in ionospheric delay is a key factor impacting the Global Navigation Satellite Systems (GNSS) positioning and navigation accuracy. We studied the effect of ionospheric delay on localizing low-cost robots. We investigated the positioning error using ionospheric delay from a GNSS receiver, IRI and our campus, KMITL, in Bangkok, to guide our ‘G-LOC’ robot. There were eight target points, set from 3 to 50 m at the same meridian with varying latitudes. Impacts on a robot moving on low solar activity days, high solar activity days, daytime, and nighttime were measured over 12 months in 2023. We found that high solar activity day impacts a robot moving on highest accuracy error up to 363 cm at high speed. In addition, we found that daytime impacts a robot moving on highest accuracy error up to 154.05 cm at high speed as well. Ionospheric delay according to high and low solar activities, and daytime, and nighttime effects on the GNSS interference transmitted to a low-cost localizing robot was expected to affect moving errors, but it did not seem to lead to a significant difference in error between the low and high solar activity days.
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Real-time GPS receiver bias estimation
(2021-09-01)
Kenpankho, Prasert
;
Chaichana, Amornchai
;
Trachu, Koson
;
Supnithi, Pornchai
;
Hozumi, Kornyanat
In this paper, we present the new method for real-time GPS receiver bias estimation by using Lagrange interpolation, which is also compared to the two current methods, polynomial and minimization of standard deviation. The estimated method is proposed to reduce the complexity and time of the GPS receiver bias estimation. Lagrange interpolation is the method to find the derivatives and integrals of discrete functions in GPS receiver bias data. The test site is located on Chumphon station, Thailand. The test period of data method is during the year 2004–2019. In the quiet and disturbed days, the polynomial method gives the highest value of the GPS receiver bias at −5.75 ns and −4.25 ns, respectively, but the Lagrange interpolation shows the lowest value of GPS receiver bias at −6.85 ns and −5.25 ns, in order. The results and comparisons among the polynomial GPS receiver bias method, the minimization of standard deviation of GPS receiver bias method, and Lagrange interpolation method show that the calculated time for Lagrange interpolation is shorter compared to other methods and it can be given more time points for finding GPS receiver biases than others.

Kenpankho, Prasert

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