Kenpankho, Prasert

Preferred name

Kenpankho, Prasert

Alternative Name

Kenpankho, P.

Main Affiliation

School of Industrial Education and Technology

prasert.ke@kmitl.ac.th

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On improvement in representation of foE in IRI
(2017-07-15)
Yang, Zhe
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Ssessanga, Nicholas
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Tran, Lan Thi
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Bilitza, Dieter
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Kenpankho, Prasert
Improvements in representation of foE for use in the International Reference Ionosphere (IRI) model are investigated. The IRI model currently depends on the 12-month running mean of sunspot number to estimate the foE. Using the F10.7 daily and F10.7_81 indices as the new model drivers, results are compared to ionosonde measurements at low, mid and high latitudes during solar minimum and solar maximum. Results show that the IRI model estimates the foE parameter better at low-mid latitudes than at high latitudes, specifically during solar maximum. Using the F10.7 indices to derive the IRI model improves estimates of foE, specifically at low-mid latitudes. The F10.7_81 index was found to perform better than the daily F10.7 index. Improvements during solar maximum and during solar minimum were on average 3.5% and 1%, respectively. Therefore, the F10.7_81 index is recommended as IRI model driver for foE estimates.
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The variation of critical frequency of E layer over Chumphon, Thailand
(2013-12-09)
Wongcharoen, Poramintra
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Kenpankho, Prasert
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Sepsirisuk, Kasemsuk
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Supnithi, Pornchai
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Noppanakeepong, Suthichai
In this research paper presents the observed critical frequency of E layer (foE) over Chumphon, Thailand which is located at nearly the magnetic equator (lat. 10.72° long. 99.37° dip. 3°) during September 2004 to August 2005. The foE is one of essential parameters in the International Reference Ionsphere (IRI) model. We investigate the variation of the observed foE by comparing to the Sun spot number, ionospheric index, and 10.7 cm. flux. Due to essentially of accurate IRI model can be used to applied in communication such as it may be implied tendency of phenomena in E layer effect on high frequency communication over Chumphon, Thailand. © 2013 IEEE.
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Study of Ionospheric Total Electron Content over Thailand Using BeiDou Satellites
(2025-01-01)
Maichuen, Samatchaya
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Keokhumcheng, Thanapon
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Kenpankho, Prasert
This study aims to analyze the Total Electron Content (TEC) in the ionosphere over Thailand using BeiDou satellite signals received by BG2s receivers, providing an alternative to the traditional use of GPS satellites for investigating TEC variations. Data were collected from January to March 2025 from six monitoring stations: Bangkok, Chiang Mai, Chumphon, Nong Bua Lam Phu, Phuket, and Ubon Ratchathani, respectively, covering the entire region of Thailand. The analysis revealed that Nong Bua Lamphu recorded the highest average at 77.94 TECU, followed by Chiang Mai with 73.55 TECU. Ubon Ratchathani had an average of 65.81 TECU, while Phuket recorded 59.54 TECU, closely followed by Bangkok with 59.22 TECU. Chumphon had the lowest average maximum value at 45.00 TECU, respectively. Additionally, training sessions were conducted for 20 participants of the Meteorological Department on using BG2s receivers to measure TEC from BeiDou satellites. The pre-training assessment showed that 6 participants, accounting for 30%, achieved scores above 80%. After the training, all participants, representing 100%, surpassed the 80% threshold. The results indicate an improvement in participants' knowledge from 30% to 100%, reflecting the success of the training program and demonstrating the potential for applying the BeiDou satellite system in future ionospheric TEC studies.
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Variation of ionospheric slab thickness observations at Chumphon equatorial magnetic location
(2011-01-01)
Kenpankho, P.
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Supnithi, P.
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Tsugawa, T.
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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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A Novel Short-Term Prediction Model for Regional Equatorial Plasma Bubble Irregularities in East and Southeast Asia
(2025-02-01)
Zhao, Xiukuan
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Li, Guozhu
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Xie, Haiyong
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Hu, Lianhuan
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Sun, Wenjie
Equatorial plasma bubble (EPB) irregularities can significantly impact satellite-based communication and navigation systems. Accurate prediction of EPB occurrence is essential for mitigating these impacts. Using the GNSS receiver network and ionosonde data from East and Southeast Asia during 2010–2021, and the rate of TEC change index to characterize the occurrence of EPB irregularities, we developed a novel Spatio-Temporal deep learning model for regional EPB irregularities short-term Prediction (STEP). The model integrates the convolutional neural network and long short-term memory (LSTM) network, together with attention mechanisms, to capture both spatial and temporal features of regional ionospheric irregularities. The results show that for 5-min forecast, the STEP model achieves a root mean square error (RMSE) of 0.062 TECU/min and an R2 of 0.818, reducing RMSE by 19.48% compared to LSTM and 27.06% compared to gated recurrent unit model. For 60-min prediction, the STEP model can still achieve reasonable accuracy with an RMSE of 0.110 TECU/min and an R2 of 0.482, showing significant improvement over traditional models. The equatorial F layer height and regional TEC fluctuations were identified as the most critical factors for predicting the generation and duration of EPB irregularities, respectively. The spatial and temporal distributions of EPB irregularities, including their latitudinal variation and delayed onset after sunset, and the occurrence across different days in East and Southeast Asia, were well predicted by the STEP. It is expected that the STEP model would provide a valuable tool for improving the resilience of GNSS against ionospheric scintillations induced by EPB irregularities.
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Improving the modeling of bottomside thickness parameters over midlatitudes and high latitudes
(2020-02-01)
Jamjareegulgarn, Punyawi
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Supnithi, Pornchai
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Kenpankho, Prasert
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Wichaipanich, Noraset
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Nayak, Chinmaya
This paper investigates bottomside thickness parameters at Digisonde stations over midlatitude and high latitude regions, and compares the diurnal, seasonal, and solar activity variations in 2014 and 2009. The geographic latitudes of high latitude considered in this work are located beyond ±60° and those of midlatitude are located between ±40° and ±60°. The IRI-modeled B0 with ABT-2009 option (B0_IRI) are also examined and compared with four kinds of the B0 values, i.e., the observed B0 (B0_obs) from GIRO, the computed B0 following to Jamjareegulgarn et al. (2017a) (B0_old), the calculated B0 with a correction factor regarding to Jamjareegulgarn et al. (2017b) (B0_new), and the B0 with an average correction factor (B0_new_c_av). The average correction factors are proposed additionally in this work so as to assist occasionally the experimental B0 nonexistence of Digisonde which are equal to 0.2658 and 0.2058 for midlatitudes and high latitudes, respectively. Results show that the diurnal variations of B0_new and B0_new_c_av are in a good agreement with those of B0_obs evidently compared with those of B0_IRI and B0_old at every station during the three seasons over high and middle latitudes. During the three seasons, the diurnal variations of B0_new_c_av show similar trends and are close to one another with the B0_obs and the B0_new with small deviations. The differences between the B0obs and the B0_new_c_av also show similar trends and are close to one another with those between the B0obs and the B0_new. In contrast, the B0_IRI with ABT-2009 option seems to predict the B0 values poorly during the three seasons at high latitudes and some seasons at midlatitudes. The proposed B0_new is useful for computing approximately the observed B0 and the ionogram-based total electron content (ITEC) of Digisonde, and the plasma scale height over midlatitudes and high latitudes.
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Comparison of e layer critical frequency over the Thai station Chumphon with IRI
(2015-04-15)
Wongcharoen, P.
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Kenpankho, P.
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Supnithi, P.
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Ishii, M.
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Tsugawa, T.
In this research, as a part of working towards improving the IRI over magnetic equatorial region, the critical frequency of E layer in the ionosphere (foE) derived from the ionogram at Chumphon station (10.72°N, 99.37°E), Thailand, during 2005-2008 is analyzed. The Chumphon station is located in the magnetic equatorial region at the magnetic latitude of 3.22°N. The seasonal variation of the foE measurements is compared to the IRI foE predictions with the optional input in the sunspot number (Rz12) and the solar radio noise flux (F10.7). For a declining phase of the solar cycle 23 during the year 2005-2008, the study shows that the IRI foE prediction is similar to the foE observation during the period of 2005-2008. The maximum differences between the IRI foE prediction and foE observation are about 500 kHz during daytime period of 2007.
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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
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Klinngam, Somjai
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Panachart, Chaiwat
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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.
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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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Galileo-E6 Bandwidth Frequency Filter Design for Galileo Receiver
(2021-09-01)
Chinnapark, Surachet
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Onanong, Narumol
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Pattameak, Julongkorn
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Mekpradab, Teerachet
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Kenpankho, Prasert
This research discusses about the combination of the LPF and HPF to perform band reject filter. Therefore, there are two combination also in designing band reject filter. The aim of this combination to get know is there have an influence on the performance of band reject filter was designed by using the frequency of the GalileoE6 with bandwidth 40 MHz. This filter is used a Butterworth filter which is presented in this study. These filter circuit is composed 4rd order. In addition to, the combination between LPF and HPF forming to a band reject filter is designed. As a result, the filter design on the frequency of Galileo-E6 is successfully used in band reject filter.

Kenpankho, Prasert

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