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Author: search.filters.author.Jamjareegulgarn, PunyawiSubject: search.filters.subject.Global Navigation Satellite System (GNSS)

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    Ionospheric-Thermospheric Responses in South America to the August 2018 Geomagnetic Storm Based on Multiple Observations
    (2022-01-01)
    Shah, Munawar
    ;
    Abbas, Ayesha
    ;
    Ehsan, Muhsan
    ;
    Aiber, Andres Calabia
    ;
    Adhikari, Binod
    The ionospheric storm time responses during August 2018 are investigated over South American region using multiple observables, for example, Global Navigation Satellite System (GNSS) derived vertical total electron content (VTEC) from International GNSS Service, magnetic field data, geomagnetic indices, global ionospheric maps, thermospheric mass density (TMD), and [O/N2] ratio measurement. Strong-ionospheric and upper-atmospheric disturbances affected the ionospheric variables with long duration during the storm recovery phase and following after. First, daytime VTEC (9:00-20:00 UT) presented variations of >15 TECU during days 25 to 30 of August 2018 in low and middle latitudes of South America, this after sudden storm commencement (SSC). Furthermore, nighttime (21:00-24:00 and 00:00-05:00 UT) VTEC presented low values (5<TECU<7) in mid-latitude region after SSC event during the main phase, followed by high values (>8 TECU) in the recovery phase. Second, the ionospheric values during the storm main phase and following after, at low-and mid-latitudes, caused the equatorial ionization anomaly to expand due to prompt penetration electric field. Furthermore, VTEC enhancements are likely to occur few hours after the SSC of 25 August 2018, while enhancements of TMD and [O/N2] ratio started to appear later on 26 and 27 of August 2018.
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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.