Climatology of ionospheric scintillations and TEC trend over the Ugandan region

Amabayo, Emirant B.; Jurua, Edward; Cilliers, Pierre J.; Habarulema, John Bosco

doi:10.1016/j.asr.2013.12.015

Cited by 27 publications

(7 citation statements)

References 22 publications

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“…Manju and Haridas (2015) observed significant asymmetry in the threshold height between the vernal equinox and autumn equinox and underlines the distinct differences in the role of neutral dynamics in ESF triggering during the two equinoxes. The local time and seasonal trends of occurrence of ionospheric irregularities observed in this study are similar to those reported in the previous studies (Aarons, 1993;Olwendo et al, 2013;Amabayo et al, 2014;Seba and Tsegaye, 2015). The occurrence of equatorial F-region irregularity has been studied, and the frequency of occurrence of equatorial spread F has been found to be higher during solar maximum (Abdu et al, 1998;Mendillo et al, 2000).…”

Section: Spatial Gradient Of T Ec(t)supporting

confidence: 89%

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Dugassa¹,

Habarulema²,

Nigussie³

2018

Preprint

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Abstract. The relation between the occurrence of ionospheric irregularity and spatial gradient of total electron content (TEC) during the post-sunset hours over the equatorial region is studied. The ionospheric irregularities could pose serious challenges to satellite-based navigation and positioning applications when trans-ionospheric signals pass through them. Different instruments and techniques have been applied to study the behavior of these ionospheric irregularities. In this study, the Global positioning system (GPS) based derived total electron content (TEC) was used to investigate the spatial gradient of TEC between two nearby stations as an indicator of the occurrence of ionospheric irregularity over the East African sector. The gradient of TEC between the two stations (ASAB: 4:34° N, 114:39° E and DEBK: 3:71° N, 109:34° E, geomagnetic) located within the equatorial region of Africa were considered in this study during the year 2014. The rate of change of TEC based derived index (ROTIave) is also used to observe the correlation between the spatial gradient of TEC and the occurrence of ionospheric irregularities. The result obtained shows that most of the maximum positive/depletions in the spatial gradient of TEC observed in March and September equinoxes are more pronounced between 19:00 LT–24:00 LT as the large-scale ionospheric irregularities do. Moreover, the observed spatial gradient of TEC shows two peaks (in March and September) and they exhibit equinoctial asymmetry where the March equinox is greater than September equinox. The enhancement in the spatial gradient of TEC and ROTIave during the 15 evening time period also show similar trends but lag 1–2 hrs from the equatorial electric field (EEF). The spatial gradient of TEC between the two nearby stations could be used as an indicator of the occurrence of ionospheric irregularities.

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Section: Spatial Gradient Of T Ec(t)supporting

confidence: 89%

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Dugassa¹,

Habarulema²,

Nigussie³

2018

Preprint

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“…By employing the horizontal wind model (HWM14), Seba et al (2018) recently reported that the difference in the wind pattern between March and September is one of the factors for the equinoctial asymmetry. The local time and seasonal trends of occurrence of ionospheric irregularities observed in this study are similar to those reported in the previous studies (Aarons, 1993;Basu et al, 1988;Olwendo et al, 2013;Amabayo et al, 2014;Seba and Tsegaye, 2015). The equinoctial asymmetries in the occurrence of ionospheric irregularities observed in our case might also be due to the direction of the meridional winds during equinoxes over the stations.…”

Section: Relation Between the Equatorial Electric Fieldsupporting

confidence: 90%

Investigation of the relationship between the spatial gradient of total electron content (TEC) between two nearby stations and the occurrence of ionospheric irregularities

2019

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Abstract. The relation between the occurrence of ionospheric irregularities and the spatial gradient of total electron content (TEC) derived from two closely located stations (ASAB: 4.34∘ N, 114.39∘ E and DEBK: 3.71∘ N, 109.34∘ E, geomagnetic), located within the equatorial region, over Ethiopia, during the postsunset hours was investigated. In this study, the Global Positioning System (GPS)-derived TEC during the year 2014 obtained from the two stations were employed to investigate the relationship between the gradient of TEC and occurrence of ionospheric irregularities. The spatial gradient of TEC (ΔTEC∕Δlong) and its standard deviation over 15 min, σ(ΔTEC∕Δlong), were used in this study. The rate of change of TEC-derived indices (ROTI, ROTIave) were also utilized. Our results revealed that most of the maximum enhancement and reduction values in ΔTEC∕Δlong are noticeable during the time period between 19:00 and 24:00 LT. In some cases, the peak values in the spatial gradient of TEC are also observed during daytime and postmidnight hours. The intensity level of σ(ΔTEC∕Δlong) observed after postsunset show similar trends with ROTIave, and was stronger (weaker) during equinoctial (solstice) months. The observed enhancement of σ(ΔTEC∕Δlong) in the equinoctial season shows an equinoctial asymmetry where the March equinox was greater than the September equinox. During the postsunset period, the relation between the spatial gradient of TEC obtained from two closely located Global Navigation Satellite System (GNSS) receivers and the equatorial electric field (EEF) was observed. The variation in the gradient of TEC and ROTIave observed during the evening time period show similar trends with EEF with a delay of about 1–2 h between them. The relationship between σ(ΔTEC∕Δlong) and ROTIave correlate linearly with correlation coefficient of C=0.7975 and C=0.7915 over ASAB and DEBK, respectively. The majority of the maximum enhancement and reduction in the spatial gradient of TEC observed during the evening time period may be associated with ionospheric irregularities or equatorial plasma bubbles. In addition to latitudinal gradients, the longitudinal gradient of TEC has contributed significantly to the TEC fluctuations.

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“…There is however asymmetry in the equinoxes, whereby the September and October crest has well‐developed double crest than the March and April crest. The trends depicted by the seasonal variation in the EIA formations are similar to those that had previously been seen in seasonal variation in TEC over this region [for example in Tariku , ; Amabayo et al ., ; Olwendo et al ., ]. It has been shown that the TEC trends also does correlate well with the solar activity indices such as the sunspot and F 10.7 indices [ Gupta and Singh , ; Bagiya et al ., ; Chen et al , ; Galav et al ., ; Liu et al ., ].…”

Section: Resultsmentioning

confidence: 99%

A study on the variability of ionospheric total electron content over the East African low‐latitude region and storm time ionospheric variations

et al. 2016

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The variation of total electron content (TEC) derived from the International Global Navigation Satellite Systems Service receiver (formerly IGS) over the East African low-latitude region from up to 12 observation stations for the period 2012 was analyzed. The diurnal and annual TEC contour plots generated from data over the region show that the equatorial anomaly crests manifest remarkable seasonal variations. The crest of the equatorial ionization anomaly is fully formed and yields the maximum values of TEC during the equinoxes (March/April and September/October) and minimum in the solstice (June/July and November/December). The results of this observation show that the crest develops between 12:00 and 16:00 LT and is greatly dependent on the time when the ionosphere is uplifted at the dip equator via the E × B drift force. The postsunset TEC enhancements at stations away from dip equator depict the ionospheric plasma density diffusion (flow) from the dip equator leading to the formation of ionization anomaly crests that lasts for few hours after the sunset local time. The ionospheric response to the strong geomagnetic storm of the March 2015 has also been examined. The ionospheric response to the geomagnetic storms has shown a strong thermosphere-ionosphere coupling. The negative storm effect that occurred over the anomaly crest region is more likely due to the composition disturbances associated with high energy deposits.

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Climatology of ionospheric scintillations and TEC trend over the Ugandan region

Cited by 27 publications

References 22 publications

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Spatial gradient of total electron content (TEC) between two nearby stations as indicator of occurrence of ionospheric irregularity

Investigation of the relationship between the spatial gradient of total electron content (TEC) between two nearby stations and the occurrence of ionospheric irregularities

A study on the variability of ionospheric total electron content over the East African low‐latitude region and storm time ionospheric variations

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