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

2018 ◽  
Author(s):  
Teshome Dugassa ◽  
John Bosco Habarulema ◽  
Melessew Nigussie
Keyword(s):  
Total Electron Content ◽  
Large Scale ◽  
Equatorial Region ◽  
Ionospheric Irregularity ◽  
Rate Of Change ◽  
Ionospheric Irregularities ◽  
Spatial Gradient ◽  
Electron Content ◽  
Total Electron ◽  
Pass Through

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.

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

2019 ◽  
Vol 37 (6) ◽  
pp. 1161-1180 ◽  
Author(s):  
Teshome Dugassa ◽  
John Bosco Habarulema ◽  
Melessew Nigussie
Keyword(s):  
Total Electron Content ◽  
Ionospheric Irregularities ◽  
Latitudinal Gradients ◽  
Spatial Gradient ◽  
Electron Content ◽  
Intensity Level ◽  
Maximum Enhancement ◽  
Total Electron ◽  
Time Period ◽  
The Relationship

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.

scholarly journals Ionospheric response to magnetar flare: signature of SGR J1550–5418 on coherent ionospheric Doppler radar

2017 ◽  
Vol 35 (3) ◽  
pp. 345-351 ◽  
Author(s):  
Ayman Mahrous
Keyword(s):  
Total Electron Content ◽  
Large Scale ◽  
Doppler Radar ◽  
Ionospheric Disturbance ◽  
Eastern Mediterranean ◽  
Small Scale ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Perturbations ◽  
Onset Phase

Abstract. This paper presents observational evidence of frequent ionospheric perturbations caused by the magnetar flare of the source SGR J1550–5418, which took place on 22 January 2009. These ionospheric perturbations are observed in the relative change of the total electron content (ΔTEC/Δt) measurements from the coherent ionospheric Doppler radar (CIDR). The CIDR system makes high-precision measurements of the total electron content (TEC) change along ray-paths from ground receivers to low Earth-orbiting (LEO) beacon spacecraft. These measurements can be integrated along the orbital track of the beacon satellite to construct the relative spatial, not temporal, TEC profiles that are useful for determining the large-scale plasma distribution. The observed spatial TEC changes reveal many interesting features of the magnetar signatures in the ionosphere. The onset phase of the magnetar flare was during the CIDR's nighttime satellite passage. The nighttime small-scale perturbations detected by CIDR, with ΔTEC/Δt  ≥  0.05 TECU s−1, over the eastern Mediterranean on 22 January 2009 were synchronized with the onset phase of the magnetar flare and consistent with the emission of hundreds of bursts detected from the source. The maximum daytime large-scale perturbation measured by CIDR over northern Africa and the eastern Mediterranean was detected after ∼ 6 h from the main phase of the magnetar flare, with ΔTEC/Δt  ≤  0.10 TECU s−1. These ionospheric perturbations resembled an unusual poleward traveling ionospheric disturbance (TID) caused by the extraterrestrial source. The TID's estimated virtual velocity is 385.8 m s−1, with ΔTEC/Δt  ≤  0.10 TECU s−1.

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