Abstract
The equatorial ionosphere is highly dynamic and consequently poses serious threats to communication and navigation systems. As a result, proper understanding of ionospheric dynamics is important. The present paper presents the results of an investigation of the correlation between quiet time vertical total electron content (VTEC) and solar quiet variation in the horizontal component of geomagnetic field (Sq(H)) from low solar activity year (2009) to the high solar activity year (2014) within the equatorial East African sector using statistical analysis method. Values of Sq(H) were observed to increase steadily from around 0700LT attaining maximum values around 1100-1200LT, then descending towards zero level and beyond. The magnitudes of (VTEC) increase uniformly from around 0600-1000LT, then gradually, attaining maximum values around 1300-1500LT. The time instants of occurrence of these peaks are mainly controlled by drifts and photo-ionization. The correlation coefficients (ccs) between (VTEC) and Sq(H) were found to be strongest during the ascending phase (0600-1200LT), ranging from 0.69 to 0.98 at Addis Ababa and 0.61 to 0.97 at Nairobi. During the descending phase (1300-1800LT), ccs range from -0.28 to 0.89 at Addis Ababa and-0.06 to 0.76 at Nairobi. A high level of significance (99.98%) of ccs was obtained. The good linear relationship is attributed to the independent increase of the eastward electric field and photo-ionization on (VTEC) while poor relationship is possibly due to domination of photo-ionization over equatorial ionization anomaly (EIA) development. The annual ccs between (VTEC) and Sq(H) exhibit a general dependence on solar activity at Addis Ababa, closer to the dip equator, rather than at Nairobi during the ascending phase of the daytime. This observation suggests that the EEJ changes linearly with change in solar activity, thus streamlining the variations in TEC, through drifts, and Sq(H) by intensifying the eastward equatorial electric field.
Highlights
The Earth’s upper atmosphere absorbs photons at wavelengths shorter than 125nm, creating conducting layers of electrons and ions that are embedded in the neutral upper atmosphere from about 60 km to 1000 km: the layers of the ionosphere (Goodman, 2005)
The values of vertical total electron content (VTEC) are plotted on the left-hand side of the y-axis along with the corresponding Sq(H ) on the right-hand side of the y-axis in each month
The statistical test of significance (t-test) of the correlation coefficients at the two stations indicates a high level of significance at 99.98%, confirming the observed relationships are significant
Summary
The Earth’s upper atmosphere absorbs photons at wavelengths shorter than 125nm, creating conducting layers of electrons and ions that are embedded in the neutral upper atmosphere from about 60 km to 1000 km: the layers of the ionosphere (Goodman, 2005). Atmospheric winds and tidal oscillations of the atmosphere compel the E-region ion International Journal of Astrophysics and Space Science 2017; 5(1): 6-18 component to move across the magnetic field lines, while electrons move much slower at right angles to both the field and neutral wind (Baumjohann and Treumann, 1996) Such relative movement constitutes an electric current and the separation of charge produces an electric field which in turn influences the current. Quiet time correlation between the variations of the horizontal (H) component of the geomagnetic field and ionospheric TEC values within the East African equatorial sector from the low solar activity year (2009) to the high solar activity year (2014) of the Solar Cycle 24 has been investigated using geomagnetic field data and corresponding co-located dual frequency GPS derived TEC data obtained from Addis Ababa (Ethiopia) and Nairobi (Kenya)
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