Equatorial F2 characteristic variability: A review of recent observations

Somoye, E.O.; Akala, A. O.; Adeniji-Adele, Rasaq Adewemimo; Iheonu, E.E.; Onori, Eugene; Ogwala, Aghogho

doi:10.1016/j.asr.2013.06.031

Cited by 6 publications

(6 citation statements)

References 21 publications

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“…Analysis was carried out by first finding the hourly monthly mean values of the h'F2 data using the statistical mean relation shown in Equation 2. Secondly the data were grouped into four different seasons comprising of three months each and were averaged to obtain their mean seasonal values using Equation 3, following the seasonal grouping used by [8], [13], [10], [35]. The seasons are December solstice (November, December and January), March equinox (February, March and April), June solstice (May, June, and July and September equinox (August, September and October).…”

Section: Methods Of Analysismentioning

confidence: 99%

Temporal and Spatial Variation of The Virtual Height of Ionosperic F2–layer Over Two Equatorial Stations During the Minimum to Ascending Phase of Solar Cycle 25

Onori,

Kayode,

Ometan

et al. 2024

AJR2P

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The research examines ionospheric F2-layer virtual height (h’F2) variations at Ilorin (14.80°N, 17.40°W) in the Africa sector and Boa Vista (2.80°N, 299.30°E) in the America sector, during Solar Cycle 25's minimum and ascending phases. The aim is to investigate the temporal and spatial variations of the virtual height of the F2-layer over two equatorial stations during the minimum to ascending phase of Solar Cycle 25 at two equatorial stations in two different longitudinal sectors. Analyzing data from these stations statistically, the paper investigates diurnal, seasonal, and annual variations in h’F2.Diurnally, the h’F2 demonstrates greater responsiveness during daytime (06:00 – 18:00 LT) compared to nighttime (18:00 – 05:00 LT). Seasonally, peak values occur around noon and post-noon periods, displaying significant disparities during equinoxes and solstices over both stations in the different solar phases. During the minimum phase year (2020), peak heights of h’F2 reached 387 km at Ilorin and 372 km at Boa Vista. In the ascending phase year (2021), these peaks slightly shifted to 389 km at Ilorin and 404 km at Boa Vista. Annually, the highest peak values of h’F2 occur at noon, measuring 376 km at Ilorin and 331 km at Boa Vista during the minimum phase, while during the ascending phase, both stations recorded almost identical values of 305 km at noon. Overall, h’F2 variation exhibited higher magnitude at Ilorin in the African longitudinal sector than at Boa Vista in the American longitudinal sector during the minimum phase of solar cycle 25, with the reverse observed during the ascending phase. This detailed analysis illuminates the complex variations in ionospheric behavior across various time frames and geographic locations, showcasing substantial variability and sensitivity to solar influences in equatorial stations across Africa and America.

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Section: Methods Of Analysismentioning

confidence: 99%

Temporal and Spatial Variation of The Virtual Height of Ionosperic F2–layer Over Two Equatorial Stations During the Minimum to Ascending Phase of Solar Cycle 25

Onori,

Kayode,

Ometan

et al. 2024

AJR2P

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“…The files were unzipped and further processed using the CRX2RNX Hatanaka and Gopi or GPS_TEC developed by Dr Gopi Seemala of Boston College in Texas [19] Mean vTEC (in TEC units of 10 16 el/m 2 ) during the four seasons at both stations for all hours of the day were plotted against each hour of the day. Also, variability of vTEC is evaluated from the hourly mean (μ) of vTEC and its corresponding standard deviation (σ) by using the approach of [15], [18], [6], [22], [23], [24].…”

Section: Methodsmentioning

confidence: 99%

“…(%) = × 100 (8) This method of determining variability shows that the deviation of all daily values from the monthly mean (or median) is considered. This indicates that the whole data is used [22], [23]. Analyses of vTEC variability will also be considered on diurnal and seasonal scales.…”

Section: Methodsmentioning

confidence: 99%

Analyses of Total Electron Content Variations Over Northern and Southern Nigeria

Ogwala

2017

JRRS

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Total electron content (TEC) is a parameter of the ionosphere that produces great effect on radio signals. We present the diurnal and seasonal variations of vertical total electron content (vTEC) during the ascending phase of solar cycle 24. A moderate solar activity year (2011) with sunspot number, Rz = 55.7 is used in this study. Total electron content (TEC) deduced from the dual frequency GPS measurements obtained at two ground stations namely: ABUZ (Zaria) with longitude 7.39oE in the north and UNEC (Enugu) with longitude 7.30oE in the south are considered. Both stations are located within the same longitude and has a latitudinal difference of 4.74o in the Nigerian equatorial ionosphere (NEI). Comparison of diurnal and seasonal variations of TEC is carried out for both stations. The diurnal variation of TEC shows a steep increase starting from sunrise, reaching daytime maximum between 13 – 15 LT at UNEC and 14 – 16 LT at ABUZ, then falls to a minimum at sunset. Dawn depression occurred at the same local time of 04 LT at both stations. On a seasonal scale, Pre- and post-midnight values were highest during the Equinoxes, followed by December solstice and least in June Solstice season at ABUZ. Pre- and post-midnight values were also higher during the Equinoxes than the Solstice season at UNEC, although they are about the same range. Also, TEC values are observed to be slightly higher for all hours and seasons at Enugu in the south than Zaria in the north except during March equinox at Zaria where TEC values were higher during the daytime. This implies that there could be little variations in TEC even within the same latitudinal zone.

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“…[5], [28], [29], [25] and [30] had made use of similar variability coefficient in studying ionospheric variability at some other ionospheric stations.…”

Section: Methodsmentioning

confidence: 99%

Comparison of Diurnal and Seasonal Variability of the Critical Frequency of the F2 Layer Over Ilorin, Jicamarca and Okinawa During Minimum Solar Activity

Onori

2017

JRRS

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The ionosphere displays a wide range of variations ranging from diurnal, seasonal, annual and solar cycle variation. In this paper we present a study of the comparison of diurnal, seasonal and semiannual variation of the variability (VR) of the critical frequency of the F2 layer (foF2) over Ilorin (Lat. 8.47oN, 4.6oE, dip 4.1oS) in the African sector, Jicamarca (Lat. 11.9oS, Long.76.8oW, dip 1oN) in the American sector and Okinawa (26.3oN, 127.8oE, dip 36.8oN) in the Asian sector during solar minimum period. These stations lie within the equatorial anomaly region of the ionosphere. Diurnal analysis revealed that the critical frequency of the F2 layer is more prone to variability (VR) during the nighttime than the day time at these stations, with two characteristics peaks, post-midnight peak and pre-midnight peak. The peaks at Ilorin (20 - 43%; 16 - 25%) are observed to be higher in values than those at Jicamarca (17 - 27%; 15 - 22%) and Okinawa (22 – 39%; 15 - 30%). Seasonally, December solstice maximum was noticed at Ilorin. Semiannual analysis showed that foF2 VR is highest at Ilorin station, followed by Okinawa station and least by Jicamarca station during the nighttime. Diurnal curves of Mean foF2 revealed pre-noon and post-noon peaks at all stations, with Jicamarca having highest values for both peaks while the semiannual curves of mean foF2 values showed almost equal values for all stations. Overall, foF2 variability is highest at Ilorin and lowest at Jicamarca while for F2 layer ionization the reverse is the case.

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Equatorial F2 characteristic variability: A review of recent observations

Cited by 6 publications

References 21 publications

Temporal and Spatial Variation of The Virtual Height of Ionosperic F2–layer Over Two Equatorial Stations During the Minimum to Ascending Phase of Solar Cycle 25

Temporal and Spatial Variation of The Virtual Height of Ionosperic F2–layer Over Two Equatorial Stations During the Minimum to Ascending Phase of Solar Cycle 25

Analyses of Total Electron Content Variations Over Northern and Southern Nigeria

Comparison of Diurnal and Seasonal Variability of the Critical Frequency of the F2 Layer Over Ilorin, Jicamarca and Okinawa During Minimum Solar Activity

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