Solar quiet day ionospheric source current in the West African region

Obiekezie, T. N.; Okeke, F. N.

doi:10.1016/j.jare.2012.09.004

Cited by 6 publications

(5 citation statements)

References 9 publications

(7 reference statements)

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“…This night variation is in line with the earlier works of [14-16, 21, 22, 30-32]. Obiekezie and Okeke [16] attributed the observed nighttime variations to currents flowing in the magnetosphere (such as the ring currents) in which most of it filter into the ionosphere at night even during magnetic quiet periods.…”

Section: Resultssupporting

confidence: 91%

“…Hasegawa [8] examined the day-to-day changes of the quiet day variation and the ionospheric current systems for the second polar year and suggested that some or all the dayto-day variabilities in solar quiet daily variation (Sq) are due to variability in the positions of the foci of the ionospheric current systems rather than changes in the distribution of ionization and conductivity. Studies conducted by [9][10][11][12][13][14][15][16] clearly showed that the variability of Sq occurred at all hours of the day.…”

Section: Introductionmentioning

confidence: 99%

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Day-to-Day Variability of H and Z Components of the Geomagnetic Field at the African Longitudes

2013

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The Day-to-day variability of the geomagnetic field elements at the African longitudes has been studied for the year 1987 using geomagnetic data obtained from four different African observatories. The analysis was carried out on solar quiet days using hourly values of the Horizontal, , and vertical, , geomagnetic field values. The results of this study confirm that Sq is a very changeable phenomenon, with a strong day-to-day variation. This day-to-day variation is seen to be superimposed on magnetic disturbances of a magnetospheric origin.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Day-to-Day Variability of H and Z Components of the Geomagnetic Field at the African Longitudes

2013

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“…This is found to be in agreement with Campbell et al (1993) who found the solsticial currents to be higher than the equinoctial currents. It also is contrary to the works of Obiekezie and Okeke (2013) that earlier observed their maximum peak in the month of March within the West Africa region. The Sq generation is affected generally by the transport of the ionization and the solar ionization at E region altitudes in mid and low latitude regions.…”

Section: Discussioncontrasting

confidence: 99%

“…The observed current patterns are the same throughout the stations and quite opposite to the patterns observed by Obiekezie and Okeke (2010). This could have arisen from the fact that Obiekezie and Okeke (2010) worked on the western African region around the dip equator whereas the present study was carried out within the Southern African region which has different geological properties.…”

Section: Discussioncontrasting

confidence: 63%

Contribution of solar quiet (Sq) daily current variations to the deep earth conductivity within the Southern African Region

Ngozi,

Francisca,

Igwe

2023

Int. J. Phys. Sci.

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This work focuses on determining the source current systems by applying the method of spherical harmonic analysis (SHA) to geomagnetic field data obtained from ground measurements. The objectives are to establish the mantle conductivity-depth profile and to compare the results of the profiles from four stations with other research findings. The study utilizes magnetometer data obtained for the year 2011 from geomagnetic stations located in Hermanus, Maputo, Tsumeb, and Hartebeesthoek within the Southern African region. The Gauss SHA method, along with Matlab software, is employed to separate the internal and external field contributions to solar quiet (Sq) current variations. Subsequently, a transfer function is used to calculate the electrical conductivity-depth profile of the region. The results show that, across all the stations, the highest seasonal Sq current was recorded in the month of June for Hartebeesthoek, Hermanus, and Tsumeb regions. Maputo, however, exhibited an exception with nearly triple peaks in the months of March, June, and December, with the highest occurring during the December solstice. The evaluated maximum values for seasonal Sq current in Hartebeesthoek, Hermanus, Maputo, and Tsumeb are approximately 16.0, 12.5, 12.0, and 14.8 nT, respectively. An equinoxial maximum with a value of 2.1 × 103 A was observed in the seasonal external Sq current in March within the Maputo region, while a solsticial minimum with a value of 0.75 × 103 A occurred in June in the Hartebeesthoek region. The seasonal separated external Sq current system pattern appears to be the same as that of the seasonal Sq current system, indicating that the source of the Sq current system is external to the Earth. The study reveals the greatest depth of Sq current penetration and the highest electrical conductivity values within the Southern African region when compared with other research. Finally, this research contributes to establishing the electrical conductivity of Maputo and Hartebeesthoek regions, where no prior work has been conducted.

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“…There are different viewpoints on the issue of day‐to‐day variability in the solar quiet daily variation ( S q ). Obiekezie and Okeke () proposed that this day‐to‐day variability can be attributed to variabilities of the ionospheric process and physical structures, such as conductivity and wind structures. However, Hasegawa (1950) suggested that the day‐to‐day variability in S q is due to variability in the positions of the foci of the ionospheric current systems rather than changes in the distribution of ionization and conductivity.…”

Section: Discussionmentioning

confidence: 99%

Anomalous phenomena in DC–ULF geomagnetic daily variation registered three days before the 12 May 2008 Wenchuan <i>M</i><sub>S</sub> 8.0 earthquake

Wang

et al. 2019

Earth and Planetary Physics

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The hourly data of the vertical Z and the horizontal H components of 37 ground–based DC–ULF geomagnetic stations are examined during 20 April–12 May 2008. On 9 May 2008, three days before the WenchuanM S 8.0 shock, anomalies — a double low‐point and a decreased amplitude — are registered on the curves of the Z component at 25 stations in a large‐scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low‐point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift (Tzs ) between the first low‐point on May 9 and the minimum point occurring time of May 1–5, 2008 is also checked. The results show that Tzs is on the order of 1–2 hours earlier or later than usual and there is a 2–6 hours’ gap between these two low‐points. However, there is still a transition area which includes the epicenter where Tzs = 0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth–air–ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above‐related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan M S 8.0 earthquake.

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Solar quiet day ionospheric source current in the West African region

Cited by 6 publications

References 9 publications

Day-to-Day Variability of H and Z Components of the Geomagnetic Field at the African Longitudes

Day-to-Day Variability of H and Z Components of the Geomagnetic Field at the African Longitudes

Contribution of solar quiet (Sq) daily current variations to the deep earth conductivity within the Southern African Region

Anomalous phenomena in DC–ULF geomagnetic daily variation registered three days before the 12 May 2008 Wenchuan <i>M</i><sub>S</sub> 8.0 earthquake

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