Statistical analysis of travelling ionospheric disturbances during geomagnetic storms
- Authors: Mothibi, Matsobane Alex
- Date: 2025-04-02
- Subjects: Sudden ionospheric disturbances , Geomagnetic storm , Solar flares , Global Positioning System , Gravity waves
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/479138 , vital:78264
- Description: This thesis presents observations of medium to large-scale traveling ionospheric disturbances (TIDs) originating from high latitudes, and propagating towards the equator and TIDs originating from the equator with a poleward propagation in the African-European sector during geomagnetically disturbed conditions between 2006 and 2022. 196 TID activities propagating over the African-European sector were observed, of these TID activities, 161 and 33 were observed during geomagnetic storms, and simultaneous occurrence of geomagnetic storms and solar flares, respectively. Total electron content perturbations derived from Global Navigation Satellite Systems (GNSS) observations within a latitude range of 40°S–60°N and longitude ranges of 20°-40°E representing the African-European sector were analysed based on the storm criteria of Dst ≤ -30 nT. The GNSS total electron content (TEC) data were used to obtain the two dimensional (2d) TEC perturbations. The northern hemispheric part of the African sector has limited data coverage which is visualized by a gap around 20°, where there were no data coverage can be observed in the 2d TEC maps. An important result is that large-scale TIDs (LSTIDs) and medium-scale TIDs (MSTIDs) were found to occur predominantly during the main and recovery phases of geomagnetic storms respectively, at least over the African-European sector. During the main phase of storms equatorward LSTID activity was relatively consistent across both hemispheres, with years of solar maximum, between 2013 and 2015, showing higher frequencies of events. Equatorward MSTID activity appeared less frequent overall, particularly in the southern hemisphere (SH), suggesting that equatorward LSTID activity are more prominent during the main phase of geomagnetic storms. Poleward TID activity were more predominant in the recovery phase than the main phase of geomagnetic storms. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2025
- Full Text:
- Date Issued: 2025-04-02
- Authors: Mothibi, Matsobane Alex
- Date: 2025-04-02
- Subjects: Sudden ionospheric disturbances , Geomagnetic storm , Solar flares , Global Positioning System , Gravity waves
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/479138 , vital:78264
- Description: This thesis presents observations of medium to large-scale traveling ionospheric disturbances (TIDs) originating from high latitudes, and propagating towards the equator and TIDs originating from the equator with a poleward propagation in the African-European sector during geomagnetically disturbed conditions between 2006 and 2022. 196 TID activities propagating over the African-European sector were observed, of these TID activities, 161 and 33 were observed during geomagnetic storms, and simultaneous occurrence of geomagnetic storms and solar flares, respectively. Total electron content perturbations derived from Global Navigation Satellite Systems (GNSS) observations within a latitude range of 40°S–60°N and longitude ranges of 20°-40°E representing the African-European sector were analysed based on the storm criteria of Dst ≤ -30 nT. The GNSS total electron content (TEC) data were used to obtain the two dimensional (2d) TEC perturbations. The northern hemispheric part of the African sector has limited data coverage which is visualized by a gap around 20°, where there were no data coverage can be observed in the 2d TEC maps. An important result is that large-scale TIDs (LSTIDs) and medium-scale TIDs (MSTIDs) were found to occur predominantly during the main and recovery phases of geomagnetic storms respectively, at least over the African-European sector. During the main phase of storms equatorward LSTID activity was relatively consistent across both hemispheres, with years of solar maximum, between 2013 and 2015, showing higher frequencies of events. Equatorward MSTID activity appeared less frequent overall, particularly in the southern hemisphere (SH), suggesting that equatorward LSTID activity are more prominent during the main phase of geomagnetic storms. Poleward TID activity were more predominant in the recovery phase than the main phase of geomagnetic storms. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2025
- Full Text:
- Date Issued: 2025-04-02
Statistical study of traveling ionospheric disturbances over South Africa
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
- Date Issued: 2019
- Authors: Mahlangu, Daniel Fiso
- Date: 2019
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Gravity waves , Magnetic storms
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76387 , vital:30556
- Description: This thesis provides a statistical analysis of traveling ionospheric disturbances (TIDs) in South Africa. The velocities of the TIDs were determined from total electron content (TEC) maps using particle image velocimetry (PIV). The periods were determined using Morlet function in wavelet analysis. The TIDs were grouped into four categories: daytime, twilight, nighttime TIDs, and those TIDs that occurred during magnetic storms. It was found that daytime medium scale TIDs (MSTIDs) propagated equatorward in all seasons (summer, autumn, winter, and spring), with velocities of about 114 to 213 m/s. Their maximum occurrence was in winter between 15:00 and 16:00 LT. The daytime large scale (TIDs) LSTIDs propagated equatorward with velocities of approximately 455 to 767 m/s. Their highest occurrence was in summer, between 12:00-13:00 LT. Most of the these TIDs (about 78%) were observed during the passing of the morning solar terminator. This implied that the morning terminator was more effective in instigating TIDs. Only a few nighttime TIDs were observed and therefore their behavior could not be statistically inferred. The TIDs that occurred during magnetically disturbed conditions propagated equatorward. This indicated that their source mechanism was atmospheric gravity waves generated at the onset of geomagnetic storms.
- Full Text:
- Date Issued: 2019
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