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On the Relationship between Low Latitude Scintillation Onset and Sunset Terminator over Africa. REMOTE SENSING 2021. [DOI: 10.3390/rs13112087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The solar terminator is a moving boundary between day-side and night-side regions on the Earth, which is a substantial source of perturbations in the ionosphere. In the vicinity of the solar terminator, essential parameters like S4 index measurements are widely analyzed in order to monitor and predict perturbations in the ionosphere. The utilization of the scintillation index S4 is a well-accepted approach to describe the amplitude/intensity fluctuation of a received signal, predominantly caused by small-scale irregularities of the ionospheric plasma. We report on the longitudinal daily and seasonal occurrence of GNSS signal scintillations, using the data derived from the GNSS stations in Bahir Dar, Ethiopia, Lomé, Togo and Dakar, Senegal. The observed seasonal climatology of GNSS signal scintillations in equatorial Africa is adequately explained by the alignment of the solar terminator and local geomagnetic declination line. It should be pointed out that the strongest scintillations are most frequently observed during the time when the solar terminator is best aligned with the geomagnetic declination line. At all three stations, the comparison of computational and observational results indicated that the scintillation activity culminated around equinoxes in the years 2014, 2015 and 2016. Comparatively, the western equatorial Africa sector has the most intense, longest-lasting, and highest scintillation occurrence rate in equinoctial seasons in all three years. For the first time, we show that the seasonal variation of the scintillation peaks changes systematically from west to east at equatorial GNSS stations over Africa. A detailed analysis of the solar day–night terminator azimuth at ionospheric heights including the time equation shows that the scintillation intensity has a maximum if the azimuth of the terminator coincides with the declination line of the geomagnetic field. Due to the remarkable change of the declination by about 10° at the considered GNSS stations, the distance between scintillation peaks increases by 46 days when moving westward from the Bahir Dar to the Dakar GNSS station. The observations agree quite well with the computational results, thus confirming Tsunoda’s theory.
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Crain DJ, Heelis RA, Bailey GJ, Richmond AD. Low-latitude plasma drifts from a simulation of the global atmospheric dynamo. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/92ja02196] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Whalen JA. Appleton anomaly increase following sunset: Its observed relation to equatorialFlayer E × B drift velocity. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98ja00104] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Sastri JH, Abdu MA, Batista IS, Sobral JHA. Onset conditions of equatorial (range) spreadFat Fortaleza, Brazil, during the June solstice. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97ja02166] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Oyama KI, Abdu MA, Balan N, Bailey GJ, Watanabe S, Takahashi T, de Paula ER, Batista IS, Isoda F, Oya H. High electron temperature associated with the prereversal enhancement in the equatorial ionosphere. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/96ja02705] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abdu M, Batista I, Walker G, Sobral J, Trivedi N, de Paula E. Equatorial ionospheric electric fields during magnetospheric disturbances: local time/longitude dependences from recent EITS campaigns. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0021-9169(94)00123-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Su Y, Bailey G, Balan N. Modelling studies of the longitudinal variations in TEC at equatorial-anomaly latitudes. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0021-9169(94)e0008-b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Balan N, Jayachandran B, Balachandran Nair R, Namboothiri S, Bailey G, Rao P. HF Doppler observations of vector plasma drifts in the evening F-region at the magnetic equator. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0021-9169(92)90162-e] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abdu MA, Batista IS, Sobral JHA. A new aspect of magnetic declination control of equatorial spread F and F region dynamo. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92ja00826] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goel MK, Singh SS, Rao BCN. Postsunset rise of F layer height in the equatorial region and its relation to the F layer dynamo polarization fields. ACTA ACUST UNITED AC 1990. [DOI: 10.1029/ja095ia05p06237] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Namboothiri SP, Balan N, Rao PB. Vertical plasma drifts in the F region at the magnetic equator. ACTA ACUST UNITED AC 1989. [DOI: 10.1029/ja094ia09p12055] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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