Observations in equatorial anomaly region of total electron content enhancements and depletions

Dashora, N.; Pandey, R.

doi:10.5194/angeo-23-2449-2005

Cited by 66 publications

(47 citation statements)

References 31 publications

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“…This is an indication of the complexity in the dynamical nature of the ionospheric condition at the equatorial region due to the effects of the equatorial electroject (EEJ) on the geomagnetic field [6] which enhances the eastward current flow within ±3 • of the magnetic equator. In addition, the depletion in TEC due to plasma instabilities after sunset is also noticed to occur consistently around 21:00 LT which is contrast to the observations of Dashora and Pandey [5] in the Asian sector where it occurred around 23:00 LT probably due to longitudinal difference and the drift of the EEJ. Figure 4 is the international reference ionosphere (IRI) model of the TEC on the days considered.…”

Section: Resultscontrasting

confidence: 83%

“…The scintillations were observed at about 21:00 LT corresponding to when there was TEC depletion in agreement with [5] Generally, the minimum value of the index was observed to coincide when the elevation angle of the satellite is higher and this confirms the angular dependence of the index. This is because at lower elevation angles, there would be the contribution from multipath fluctuations due to ground-based reflectors that obstruct the sky.…”

Section: Resultssupporting

confidence: 78%

“…This continues afterwards till about midnight and minor enhancement in TEC values was also noticed. These fluctuations in TEC values are probably due to the precipitating effects of the rising plasma plumes or bubbles in the ionosphere at the equatorial anomaly region as observed by Valladares et al [9] and Dashora and Pandey [5].…”

Section: Resultsmentioning

confidence: 79%

“…This is because at lower elevation angles, there would be the contribution from multipath fluctuations due to ground-based reflectors that obstruct the sky. According to Dashora and Pandey [5], the scintillation index greater than 0.2 is considered to imply a significant level of scintillation. The occurrence of high scintillation index during nighttime period according to [12] and [21] can be ascribed to the rising of plasma bubbles (from the F-layer of the ionosphere) at the magnetic equator to the topside of the ionosphere to produce scintillations in patches.…”

Section: Resultsmentioning

confidence: 99%

“…The study of ionospheric condition using GPS measurements in the equatorial regions of the world, including South America and Asia has been reported widely by [5][6][7][8][9] among others. Not until recently, similar efforts over the African equatorial regions have been scanty or very few if it existed.…”

Section: Introductionmentioning

confidence: 99%

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Diurnal Variation of TEC and S 4 Index During the Period of Low Geomagnetic Activity at Ile-Ife, Nigeria

Ariyibi

Doherty

Coster³

et al. 2013

Arab J Sci Eng

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Ile-Ife lies on the equatorial anomaly region where the ionospheric current is greatly influenced by the existence of the equatorial electrojet. The dual frequency SCINDA NovAtel GSV 4004B GPS receiver recently installed at Ile-Ife [on geographical latitude 7 • 33 N and longitude 4 • 33 E and geomagnetic dipole (coordinate) of latitude 9.84 • N and longitude 77.25 • E] is currently operational and recording data from the available global positioning system satellites. The receiver provides the data on total electron content (TEC) and the scintillation index (S 4 ). This paper presents the first sets of results from this station. Data records for the month of February 2010 were analyzed using the WinTec-P software program and these were interpreted to discuss the diurnal variation of the TEC and S 4 index during the period considered, as having low geomagnetic activity. The vertical TEC in this study showed that the values vary widely from as low as 0 TECu about sunrise to about 35 TECu during the day. Depletion in TEC was also noticed about sunset and marked by the occurrence of scintillations with a maximum index value of 0.3. Results of the IRI models and the observed TEC differ considerably; hence, there is the need to improve IRI models for its adaptability to the Africa ionospheric conditions.

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Section: Resultscontrasting

confidence: 83%

Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Diurnal Variation of TEC and S 4 Index During the Period of Low Geomagnetic Activity at Ile-Ife, Nigeria

Ariyibi

Doherty

Coster³

et al. 2013

Arab J Sci Eng

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Ionospheric response to the geomagnetic storm of 15 May 2005 over midlatitudes in the day and night sectors simultaneously

Galav

Rao

Sharma³

et al. 2014

JGR Space Physics

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The ionospheric response to the geomagnetic storm of 15 May 2005 has been studied over midlatitude stations in the dayside and nightside, simultaneously. In the day side the ionospheric response has been studied using the ground-based GPS and ionosonde measurements from the stations POL2 and Alma-Ata, respectively. The dayside total electron content (TEC) and f o F 2 variations are characterized by two well-separated enhancements. Of which the first enhancement in both the parameters is attributed to the episode of prompt penetration electric field caused by the sudden southward turning of interplanetary magnetic field (IMF) B z around 0600 UT. The second enhancement which was also superposed by wave like modulations has been attributed to the storm-induced winds. The maximum peak-to-peak amplitude of modulation in TEC is found to be 5 TECU (total electron content unit, 1 TECU = 10 16 el m À2). The enhanced plasma density observed during the daytime at midlatitudes is found to be locally produced and not transported from the equatorial ionization anomaly region because the time of enhanced plasma density at midlatitude is earlier than that observed at low latitudes. During the storm main phase, the nightside GPS observations from the midlatitude station ALGO (Algonquin Park, Canada) show moderate to large TEC fluctuations and short duration depletions that occur in a narrow latitude zone. These fluctuations and depletions in TEC have been attributed to the combined effect of storm-induced equatorward movement of the midlatitude ionospheric trough due to the expansion of auroral oval and the storm time-enhanced density. The maximum amplitude of the TEC depletions is found to be of the order of 20 TECU. Rate of TEC Index is also found to be high with a maximum value of 2.

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Probing the possible trigger mechanisms of an equatorial plasma bubble event based on multistation optical data

Taori

Parihar²,

Ghodpage

et al. 2015

JGR Space Physics

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We analyze an equatorial plasma bubble (EPB) event observed in optical 630 nm image data simultaneously from Gadanki (13.5°N, 79.2°E), Kolhapur (16.8°N, 74.2°E), India. The total electron content data from Gadanki together with the ionosonde data from an equatorial Indian station, Tirunelveli (8.7°N, 77.8°E) confirmed the association of observed EPB event with equatorial spread F (ESF). The optical 630 nm images from a farther low‐latitude Indian station Ranchi (23.3°N, 85.3°E) show clear signatures of tilted east‐west wave structures propagating toward equator. Further, the upward wave energy noted in mesospheric airglow data was found to be negligible. These data suggest that possibly the off‐equatorial tilted east‐west structures triggered the observed EPB/ESF event.

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Observations in equatorial anomaly region of total electron content enhancements and depletions

Cited by 66 publications

References 31 publications

Diurnal Variation of TEC and S 4 Index During the Period of Low Geomagnetic Activity at Ile-Ife, Nigeria

Diurnal Variation of TEC and S 4 Index During the Period of Low Geomagnetic Activity at Ile-Ife, Nigeria

Ionospheric response to the geomagnetic storm of 15 May 2005 over midlatitudes in the day and night sectors simultaneously

Probing the possible trigger mechanisms of an equatorial plasma bubble event based on multistation optical data

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