https://vital.seals.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 Modelling storm-time TEC changes using linear and non-linear techniques https://vital.seals.ac.za/vital/access/manager/Repository/vital:30762 4. The performance evaluation of MIDAS compared with ANNs to reconstruct storm-time TEC over the African low- and mid-latitude regions showed that MIDAS and ANNs provide comparable results. Their respective mean absolute error (MAE) values were 4.81 and 4.18 TECU. The ANN model was, however, found to perform 24.37 % better than MIDAS at estimating storm-time TEC for low latitudes, while MIDAS is 13.44 % more accurate than ANN for the mid-latitudes. When their performances are compared with the IRI model, both MIDAS and ANN model were found to provide more accurate storm-time TEC reconstructions for the African low- and mid-latitude regions. A comparative study of the performances of EOF, NLRA, ANN, and IRI models to estimate TEC during geomagnetic storm conditions over various latitudes showed that the ANN model is about 10 %, 26 %, and 58 % more accurate than EOF, NLRA, and IRI models, respectively, while EOF was found to perform 15 %, and 44 % better than NLRA and IRI, respectively. It was further found that the NLRA model is 25 % more accurate than the IRI model. We have also investigated for the first time, the role of meridional neutral winds (from the Horizontal Wind Model) to storm-time TEC modelling in the low latitude, northern and southern hemisphere mid-latitude regions of the African sector, based on ANN models. Statistics have shown that the inclusion of the meridional wind velocity in TEC modelling during geomagnetic storms leads to percentage improvements of about 5 % for the low latitude, 10 % and 5 % for the northern and southern hemisphere mid-latitude regions, respectively. High-latitude storm-induced winds and the inter-hemispheric blows of the meridional winds from summer to winter hemisphere have been suggested to be associated with these improvements.]]> Wed 12 May 2021 19:12:42 SAST ]]> Addressing flux suppression, radio frequency interference, and selection of optimal solution intervals during radio interferometric calibration https://vital.seals.ac.za/vital/access/manager/Repository/vital:38663 Wed 12 May 2021 17:37:38 SAST ]]> PyMORESANE: A Pythonic and CUDA-accelerated implementation of the MORESANE deconvolution algorithm https://vital.seals.ac.za/vital/access/manager/Repository/vital:5563 Wed 12 May 2021 16:14:42 SAST ]]> Statistical Analysis of the Radio-Interferometric Measurement Equation, a derived adaptive weighting scheme, and applications to LOFAR-VLBI observation of the Extended Groth Strip https://vital.seals.ac.za/vital/access/manager/Repository/vital:30942 Wed 12 May 2021 15:54:37 SAST ]]> A pilot wide-field VLBI survey of the GOODS-North field https://vital.seals.ac.za/vital/access/manager/Repository/vital:30027 5x105 K and >6x1021 W Hz-1 respectively. This work demonstrates that automated post-processing pipelines for wide-field, uniform sensitivity VLBI surveys are feasible and indeed made more efficient with new software, wide-field imaging algorithms and more purpose-built source- finders. This broadens the discovery space for future wide-field surveys with upcoming arrays such as the African VLBI Network (AVN), MeerKAT and the Square Kilometre Array (SKA).]]> Thu 13 May 2021 05:08:27 SAST ]]>