A study on the variability of ionospheric total electron content over the East African low-latitude region and storm time ionospheric variations

The variation of total electron content (TEC) derived from the International Global Navigation Satellite Systems Service receiver (formerly IGS) over the East African low-latitude region from up to 12 observation stations for the period 2012 was analyzed. The diurnal and annual TEC contour plots generated from data over the region show that the equatorial anomaly crests manifest remarkable seasonal variations. The crest of the equatorial ionization anomaly is fully formed and yields the maximum values of TEC during the equinoxes (March/April and September/October) and minimum in the solstice (June/July and November/December). The results of this observation show that the crest develops between 12:00 and 16:00 LT and is greatly dependent on the time when the ionosphere is uplifted at the dip equator via the E × B drift force. The postsunset TEC enhancements at stations away from dip equator depict the ionospheric plasma density diffusion (flow) from the dip equator leading to the formation of ionization anomaly crests that lasts for few hours after the sunset local time. The ionospheric response to the strong geomagnetic storm of the March 2015 has also been examined. The ionospheric response to the geomagnetic storms has shown a strong thermosphere-ionosphere coupling. The negative storm effect that occurred over the anomaly crest region is more likely due to the composition disturbances associated with high energy deposits

Validation of NeQuick 2 model over the Kenyan region through data ingestion and the model application in ionospheric studies

NeQuick 2 is an ionospheric electron density model which provides electron density for a given location. Its output depends on solar activity expressed by 12-month running average sunspot number (R12) or solar radio flux (F10.7). To improve the model capabilities to reproduce electron density, data ingestion techniques have been implemented which replace the standard solar activity indices input with effective parameters that allow adapting a model to a certain data sets. In regions like the Sub-Saharan Africa where few observational data were available until recently, the performance of the ingested model needs some validation. This study investigates the performance of NeQuick 2 in the Kenya region, a low latitude region by assisting the model with total electron content measurement from a single GNSS station. These measurements are used to calculate effective ionization level parameters, which enable the difference between the measured and modeled TEC over the station to be less or equal to 0.5 TECU. The results show that by using computed effective parameters values as inputs in nearby stations, the model performance is greatly improved for both the low and moderate solar activity. This work has also demonstrated the capability of the model to describe spatial distribution of the total electron content in the low- latitude ionosphere.Published143-1532A. Fisica dell'alta atmosferaJCR Journa

Ionospheric Imaging in Africa

Accurate ionospheric specification is necessary for improving human activities such as radar detection, navigation and Earth observation. This is of particular importance in Africa, where strong plasma density gradients exist due to the equatorial ionization anomaly. In this paper the accuracy of three-dimensional ionospheric images is assessed over a two-week test period (2–16 December 2012). These images are produced using differential Global Positioning System (GPS) slant Total Electron Content (TEC) observations and a time-dependent tomography algorithm. The test period is selected to coincide with a period of increased GPS data availability from the African geodetic REference Frame (AFREF) project. A simulation approach that includes the addition of realistic errors is employed in order to provide a ground truth. Results show that the inclusion of observations from the AFREF archive significantly reduces ionospheric specification errors across the African sector, but especially in regions that are poorly served by the permanent network of GPS receivers. The permanent network could be improved by adding extra sites and by reducing the number of service outages that affect the existing sites