Characterization of GNSS scintillations over Lagos, Nigeria during the minimum and ascending phases (2009–2011) of solar cycle 24

Statistics of GNSS amplitude scintillation occurrences over Dakar, Senegal, at varying elevation angles during the maximum phase of solar cycle 24

“…In modern GNSS receivers, internal noises are being optimally reduced by the use of highly stable oscillators (e.g., oven‐controlled crystal oscillator, OCXO). Conventionally, ionospheric scintillation data processing for scientific investigations usually adopts a 30° elevation masking, with a view to suppressing multipath effects [ Cervera and Thomas , ; Akala et al ., , ]. The drawback of this multipath filtering procedure is that ionospheric‐induced scintillation data at low‐elevation masking are lost during filtering.…”

GPS Amplitude Scintillations over Kampala, Uganda, During 2010–2011

“…1 and 2, scintillations are observed during post-sunset hours, decaying around midnight. We attributed the post sunset occurrences of scintillations to ionospheric density, largely dependent on the electric field, recombination rate and the neutral winds (Titheridge 1995, Akala et al 2014. During the period of local sunset in the equatorial region, the zonal neutral wind and the rapid decay of the E region density interact to develop an enhanced eastward electric field on the day-side of the terminator and a westward electric field on the night-side (Rishbeth et al 1963, Woodman 1970, Kelley 1989, Anderson and Haerendel 1979, Heelis 2004.…”

“…The enhanced eastward electric field (pre-reversal enhancement, PRE, in the zonal electric field) causes vertical upwelling of the F region and steepens the bottom side density gradient to trigger the Rayleigh-Taylor instability (Kelley 1989). Consequently, the low density plasma from the bottom side percolates into the topside ionosphere to develop a plethora of plasma bubbles that transform to a cascade of irregularities of different scale sizes and cause scintillation of radio signals (Basu et al 2002, Valladares et al 2004, 2014.…”

“…2010 was a year of minimum solar activity, with average annual sunspot numbers Rz; 18, while 2011 was a year of ascending solar activity (solar cycle 24), with annual sunspot number Rz; 50. In order to reduce multipath effects, only data from satellites with elevation angles greater than 30° were used (Akala et al 2011(Akala et al , 2014. Each one-minute event was characterized by the data from satellite which provided the highest scintillation index.…”

“…The progressive efforts made over the past years to support global understanding of the underlying physics behind the formation of ionospheric irregularities are still being challenged by data gaps, due to uneven global distributions of ionospheric sensors, particularly in the equatorial region of Africa (Akala et al 2014). However, the situation is being assuaged by the recent concerted installations of instruments at many locations across Africa, upon which ionospheric results from African sector are now presented to the scientific community.…”