Ionospheric impact of severe space weather events on GNSS measurements from Thailand | |
| Author | Chowdhary, V. Rajesh |
| Call Number | AIT Diss. no.RS-15-01 |
| Subject(s) | Space environment--Remote sensing Ionospheric research Solar activity |
| Note | A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Remote Sensing and Geographic Information Systems |
| Publisher | Asian Institute of Technology |
| Abstract | As the sun is approaching its solar maximum, the solar activity is observed to be increasing rapidly due to its 11 year solar cycle. The increase in solar activity adversely affects Earth‘s Ionosphere and GPS signals reaching ground based receivers. That can be a major threat to GPS users worldwide. This dissertation presents a study of effects of solar activities on ionosphere‘s Total Electron Content(TEC)using GPS-SCINDA station‘s data from Thailand region. The data used are the vertical TEC (vTEC) observed at the Bangkok (AIT, 14.079 N, 100.612 E) and Chiang Mai University (CMU, 18.480 N, 98.570 E). AIT and CMU stations are located at 4.13º N and 8.61º N magnetic latitude respectively, a region of intense equatorial ionospheric disturbances. This study is based on data from both stations for the period August 2010–July 2012. A brief comparison of both stations vTEC variations has been presented. During the period of study new sunspot regions were observed to be forming on the surface of the sun. Also the geomagnetic indices have exhibited an intense phenomenon due to severe space weather events. The phenomenon of TEC depletions and enhancements were observed and studied in depth during the period of research. This research also contributed to analyze the longitudinal and latitudinal variations of vTEC in the study region. The result shows very intense variations in TEC were during severe events. Also, diurnal, seasonal and annual variations of vTEC for both stations for the period of study were modelled and analyzed. And newly introduced International Reference Ionosphere-2012 (IRI-2012) model data has been utilized and compared to the GPS TEC data obtained at the both stations. Data comparison lead to the Model validation of newly released IRI-2012 version and also able to foresee the issues occurring when dealt with data over equatorial ionsopheric anomaly (EIA) region. The key contributions of the dissertation could include: 1. From the data of TEC obtained from both stations, it can be inferred that TEC peak was observed during 06:00 UT–12:00 UT diurnally. These results are consistently in agreement with those obtained from earlier similar works. 2. It has been proven from the analysis, of both stations data that the case of TEC varies as one move away from the equatorial region. Comparing both stations maximum TECU values gives a clear conclusion that prominently CMU station experiences higher TEC values than AIT during the same period. This difference can be due to formation of ionization crest exactly above the CMU station. 3. From this study it can be stated that there exists a substantial influence of solar flare photons or CME related geomagnetic storms on the behaviour of total electron content over Thailand region. 4. IRI-2007 and IRI-2012 models have been validated by using the TEC data retrieved from the CMU station. And correlation of data has been observed to be 0.9%,which proves to be positive with the IRI-2012 model for 2012 TEC data for CMU station. 5. The performance of the IRI model depends on the year of the data chosen for the data validation. It is recommended to use IRI-2012 model for the data from the year 2012 onwards than IRI-2007. 6. This dissertation contributes to the first in its kind to perform data modelling and analysis on GPS-SCINDA stations data in Thailand region. The data modelling and data analysis of GPS-SCINDA station‘s data has facilitated the thorough understanding of equatorial ionospheric motions as a function of diurnal, seasonal, annual, solar cycle and latitude. |
| Year | 2015 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Remote Sensing (RS) |
| Chairperson(s) | Tripathi, Nitin Kumar;Nakamura, Shinichi |
| Examination Committee(s) | Taravudh Tipdecho;Soni, Peeyush;Raju, Durairaju Kumaran;Yizengaw, Endawoke; |
| Scholarship Donor(s) | Government of Japan; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2015 |