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Author: search.filters.author.Seechai, Khanitin

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    Simultaneous equatorial plasma bubble observation using amplitude scintillations from GNSS and LEO satellites in low-latitude region
    (2023-12-01)
    Seechai, Khanitin
    ;
    Myint, Lin Min Min
    ;
    Hozumi, Kornyanat
    ;
    Nishioka, Michi
    ;
    Saito, Susumu
    This study estimates the scale sizes of the plasma density irregularities and the longitudinal width associated with equatorial plasma bubbles (EPBs) in equatorial and low-latitude regions. By analyzing amplitude scintillation S<inf>4</inf> indices and total electron content (TEC) measured from low earth orbit (LEO) satellite’s beacon signals with 400 MHz and Global Navigation Satellite System (GNSS) L1/E1 signals with 1575.42 MHz, recorded by receivers at the KMITL station in Bangkok, Thailand (geographic; 13.73° N, 100.77°E, magnetic: 7.26°N), we investigate the characteristics of these irregularities. We collected data of 154 LEO satellite pass events during nighttime on 21 disturbed days in four equinoctial months in 2021. Based on the presence or absence of the scintillation effects on GNSS and LEO beacon signals, the events are categorized into four classes to estimate the scale size of the plasma density irregularities. The analysis suggests that events with both GNSS and LEO scintillations, as well as events with GNSS scintillation alone, occur predominantly before midnight assuming the presence of the small-scale size of the irregularities within EPB. However, events with only LEO scintillation occur throughout the whole night and some events are observed before the events with both GNSS and LEO scintillations. Post-sunset LEO scintillation alone may be attributed to the onset of EPBs developing at low altitude, while post-midnight LEO scintillation events near the magnetic equator, observed during periods of low GNSS Rate of TEC Index (ROTI) values, are associated with bottom-side ionospheric irregularities but are not linked with EPB. The findings are consistent with previous researches on the generation and decay of electron density irregularities within plasma bubbles. However, this study provides new insights by using specific data sets and analysis techniques, offering a more comprehensive understanding of the association of LEO scintillations with bottom-side ionospheric irregularities near the magnetic equator, not observed in the ROTI map. Graphical Abstract: [Figure not available: see fulltext.]
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    Comparison study of amplitude scintillation between GNSS and satellite beacon receivers in Thailand
    (2022-01-01)
    Seechai, Khanitin
    ;
    Myint, Lin Min Min
    ;
    Hozumi, Kornyanat
    ;
    Supnithi, Pornchai
    Ionospheric scintillation is caused by irregular electron density in the ionosphere. Severe ionospheric scintillation can degrade the Global Navigation Satellite System (GNSS) signal quality and system performance. In low-latitude region, the phenomenon that may cause the ionospheric scintillation, called equatorial plasma bubble or EPB frequently arise. The effects of EPB on the scintillation at different frequencies and systems need to be analyzed as the study will enhance our EPB understandings. In this work, we aim to study the relationship of the amplitude scintillation index between from GNSS and satellites beacon receivers at KMITL, Thailand to determine the size and characteristics of EPB. The GNSS data were collected in March, April, September, and October 2021. From the analysis, the results show that during locally disturbed time, satellite beacon signals complement the GNSS signals to indicate EPB occurrences.
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    Statistical Analysis of Scintillation Index and ROTI based on Multi-GNSS Data at Chumphon, Thailand
    (2021-06-27)
    Seechai, Khanitin
    ;
    Jamjareegulgarn, Punyawi
    ;
    Wang, Ningbo
    ;
    Supnithi, Pornchai
    Ionospheric scintillation is caused by the fluctuation of electron density in the ionosphere. Severe ionospheric scintillation can degrade the Global Navigation Satellite System (GNSS) signal quality and performance. In low-latitude region, the phenomenon that may cause the ionospheric scintillation, called equatorial plasma bubble or EPB frequently arise. Rate of TEC change Index (ROTI) is utilized to detect the EPB occurrence. In this work, we aim to determine the relationship between the amplitude scintillation index (S4) and the rate of TEC change index (ROTI) at Chumphon, Thailand. The data are collected from a multi-constellation multifrequency GNSS receiver from 11 November to 31 December 2020. From the analysis, the results show that the percentage of enhanced ROTI and S4 events are 21.57% and 17.65%, respectively. Moreover, the statistical number of simultaneous enhancements of ROTI and S4 show the good correspondence. Refer to GALILEO and BeiDou, the S4 index of low frequency signal is disturbed more frequently than that of high frequency signal. However, this phenomenon cannot be seen in GPS.