Supnithi, Pornchai
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Supnithi, Pornchai
Alternative Name
Supnithi, P.
Supnithi, Pomchai
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pornchai.su@kmitl.ac.th
21 results
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Item type:Publication, The variation of critical frequency of E layer over Chumphon, Thailand(2013-12-09); ; ; Noppanakeepong, SuthichaiIn 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Latitudinal GRBR-TEC estimation in Southeast Asia region based on the two-station method(2014-10-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The occurrence of equatorial spread-F at conjugate stations in Southeast Asia(2015-04-15); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Total electron content observations by dense regional and worldwide international networks of GNSS(2018-06-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Identifying Geomagnetic Storms with Ionospheric Storm Scale for GNSS and Disaster Prevention(2020-03-01); ; ; ; Tangtrakunphaisan, UdomsitThis paper proposes an ionospheric storm scale (I-scale) for identifying the impact of geomagnetic or ionospheric storms in the Ionosphere for GNSS (global navigation satellite system) service and disaster prevention. The I-scale in this work is computed based on the observed foF2 at Chumphon station (10.72°N, 99.37°E) over equatorial latitude from January 2004 to July 2018. The results report that the severe geomagnetic storms, i.e., IP3 and IN3, seldom occur at Chumphon with the probabilities of 0.02% and 0.07%, respectively. The probability of quiet ionospheric condition is the maximum value of 70.73%. Meanwhile, the other I-scales sometimes occur and range from 0.60% to 13.97%. The benefits of the foF2-based I-scale are to indicate the violence level of geomagnetic storms and to announce the ionospheric irregularities in practice. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The statistics of equatorial spread-F at the conjugate stations in Southeast Asia(2014-01-01); ; Tsugawa, TakuyaIonospheric disturbance is a major impediment to current communication systems with the signals propagating through the ionosphere. A signature of such disturbance when appearing in an ionogram, resulting from the ionosonde observation system, is known as spread-F. The spread-F statistics is therefore crucial to the design and operation of communication system. In this work, we analyze the equatorial spread-F (ESF) statistics at the conjugate stations: Chiangmai, Chumphon and Kototabang during the period of minimum solar activity from September 2008 to April 2009. The statistics of range type spread-F (RSF) occurrence after the local sunset are shown in terms of the monthly average percentage since it is related to the Equatorial Plasma Bubble (ESP). We found that the RSF occurrence is higher at Chumphon station, which is near the magnetic equator, than at Kototabang and Chiangmai stations. The maximum level occurs during March 2009 at Chumphon station and the higher rate mostly during the equinoctial months. In addition, we compare the observed RSF occurrence probability at Chumphon station with the IRI-2012 model prediction. The comparison results show that the IRI model overestimates our results in all seasons, most evidently in December Solstice, except the estimation in June solstice during 21:00-03:30 LT when IRI model underestimates the statistics of RSF occurrence. Nevertheless, the IRI model gives closer probability values in March equinox during 20:00-22:00 LT than other seasons. © 2014 IEEE. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A comparison of neural network-based predictions of foF2 with the IRI-2012 model at conjugate points in Southeast Asia(2017-06-15); Tsugawa, TakuyaThis paper presents the development of Neural Network (NN) model for the prediction of the F2 layer critical frequency (foF2) at three ionosonde stations near the magnetic equator of Southeast Asia. Two of these stations including Chiang Mai (18.76°N, 98.93°E, dip angle 12.7°N) and Kototabang (0.2°S, 100.3°E, dip angle 10.1°S) are at the conjugate points while Chumphon (10.72°N, 99.37°E, dip angle 3.0°N) station is near the equator. To produce the model, the feed forward network with backpropagation algorithm is applied. The NN is trained with the daily hourly values of foF2 during 2004–2012, except 2009, and the selected input parameters, which affect the foF2 variability, include day number (DN), hour number (HR), solar zenith angle (C), geographic latitude (θ), magnetic inclination (I), magnetic declination (D) and angle of meridian (M) relative to the sub-solar point, the 7-day mean of F10.7 (F10.7_7), the 81-day mean of SSN (SSN_81) and the 2-day mean of Ap (Ap_2). The foF2 data of 2009 and 2013 are then used for testing the NN model during the foF2 interpolation and extrapolation, respectively. To examine the performance of the proposed NN, the root mean square error (RMSE) of the observed foF2, the proposed NN model and the IRI-2012 (CCIR and URSI options) model are compared. In general, the results show the same trends in foF2 variation between the models (NN and IRI-2012) and the observations in that they are higher during the day and lower at night. Besides, the results demonstrate that the proposed NN model can predict the foF2 values more closely during daytime than during nighttime as supported by the lower RMSE values during daytime (0.5 ≤ RMSE ≤ 1.0 for Chumphon and Kototabang, 0.7 ≤ RMSE ≤ 1.2 at Chiang Mai) and with the highest levels during nighttime (0.8 ≤ RMSE ≤ 1.5 for Chumphon and Kototabang, 1.2 ≤ RMSE ≤ 2.0 at Chiang Mai). Furthermore, the NN model predicts the foF2 values more accurately than the IRI model at the three sites on average, as clearly seen on the yearly RMSE averages. The RMSE values of NN model are lower than those of both CCIR and URSI options, and in terms of the yearly percentage improvements, the NN model gives improvement of around 10–15% in 2009 and 10% in 2013 for Chiang Mai, 20–25% in 2009 and 5–10% in 2013 for Chumphon, and around 18–25% in 2009 and 20–30% in 2013 at Kototabang. Although the NN model predicts the foF2 values closely to the observed data and produces more accurate prediction than the IRI models, in some cases, the IRI model performs better than the NN model. Hence, there is still room for further improvement of the proposed NN model. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Estimation of the single GPS-receiver bias using the gradient descent algorithm(2016-09-06); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Ionospheric peak height at the magnetic equator: Comparison between ionosonde measurements and IRI(2017-07-15); Komolmis, TharadolThe 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 yourconsent settings
Item type:Publication, Assessment of GPS-TEC with the IRI-2016 model, the IRI-Plas model and GIM-TEC during low solar activity at KMITL, Thailand(2019-06-01); ;