Low latitude ionospheric scintillation and zonal irregularity drifts observed with GPS-SCINDA system and closely spaced VHF receivers in Kenya

Olwendo, O.J.; Baluku, T. K.; Baki, P.; Cilliers, Pierre J.; Mito, C.; Doherty, Patricia H.

doi:10.1016/j.asr.2012.12.017

Cited by 33 publications

(21 citation statements)

References 26 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%

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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%

“…CC BY 4.0 License. seasonal occurrence of the ionospheric irregularities has been studied by the several workers (Olwendo et al, 2013(Olwendo et al, , 2016Ngwira et al, 2013;Seba and Tsegaye, 2015;Oladipo and Schuler, 2013b;Oladipo et al, 2014;Mungufeni et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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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“…Especially, given Fresnel considerations, GPS L band (1.575 GHz) scintillation is sensitive to ~ 360–400 m for an irregularity layer at 350 km in the ionosphere, and VHF (260 MHz) scintillation is sensitive to ∼1 km [ Basu et al ., ; Kintner et al ., ]. Extensive studies of the properties of VHF and GPS scintillations have been reported by many authors [e.g., Muella et al ., ; de Paula et al ., ; Olwendo et al ., ]. The observations by Yeh et al .…”

Section: Introductionmentioning

confidence: 99%

“…Especially, given Fresnel considerations, GPS L band (1.575 GHz) scintillation is sensitive to~360-400 m for an irregularity layer at 350 km in the ionosphere, and VHF (260 MHz) scintillation is sensitive to ∼1 km [Basu et al, 1978;Kintner et al, 2004]. Extensive studies of the properties of VHF and GPS scintillations have been reported by many authors [e.g., Muella et al, 2008;de Paula et al, 2010;Olwendo et al, 2013]. The observations by Yeh et al [1979] and DasGupta et al [1982] of EPBs and scintillations near the equatorial station Natal, Brazil, and Arequipa, Peru found a close correlation between EPBs and scintillations.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric plasma bubbles observed concurrently by multi‐instruments over low‐latitude station Hainan

et al. 2015

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Previous studies have shown that the ionospheric "strong range spread F" (SSF) closely correlates with the occurrence of scintillations caused by equatorial plasma bubbles. However, there is no report on concurrent observations of SSF and bubbles with in situ measurement. This paper discusses two cases of concurrent observations with a DPS4 Digisonde and a collocated scintillation monitor at the low-latitude station Hainan (19.5°N, 109.1°E), and with in situ ion density measurements made by the ROCSAT-1 satellite. Two case studies were made for 10 and 23 April 2004, respectively. In both cases, the SSF occurred before midnight and lasted more than 3.5 h. The scintillations were accompanied with strong range SF. Concurrently, the ROCSAT-1 satellite observed plasma bubbles over Hainan station. In the first case, two bubbles were observed by the satellite with east-west sizes of more than~200 km over Hainan station. Two bubbles were also observed in the second case with east-west extensions of about 220 km and 35 km, respectively. For the first time, direct observational evidence is provided for the causal relationship between equatorial plasma bubbles with in situ measurement and the concurrent occurrence of SSF and strong scintillations.

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“…The PRE is generated through the interaction of zonal neutral wind in the F region and the conductivity gradient caused by the terminator. The density gradient affects the R-T instability growth rate and thus the generation of irregularities (Ossakow, 1981;Mendillo et al, 1992). Background electron density and its distribution in the ionosphere affects the formation of ionospheric irregularities.…”

Section: Relation Between the Equatorial Electric Fieldmentioning

confidence: 99%

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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Low latitude ionospheric scintillation and zonal irregularity drifts observed with GPS-SCINDA system and closely spaced VHF receivers in Kenya

Cited by 33 publications

References 26 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

Ionospheric plasma bubbles observed concurrently by multi‐instruments over low‐latitude station Hainan

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

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