http://vital.seals.ac.za:8080/vital/access/manager/Index ${session.getAttribute("locale")} 5 Modeling and measurement of torqued procession in radio pulsars http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5475 Wed 27 Oct 2021 10:07:08 SAST ]]> Influence of argon ion implantation on the thermoluminescence properties of aluminium oxide http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:50173 Wed 20 Jul 2022 09:15:38 SAST ]]> Combined spectral and stimulated luminescence study of charge trapping and recombination processes in α-Al2O3:C http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:28235 Wed 15 Sep 2021 14:30:53 SAST ]]> Classical and quantum picture of the interior of two-dimensional black holes http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:20531 Wed 12 May 2021 23:48:00 SAST ]]> Some ionospheric effects observed at sunrise http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5513 Wed 12 May 2021 23:37:53 SAST ]]> The development and evaluation of a Nd:YAG laser incorporating an unstable resonator http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5512 Wed 12 May 2021 23:35:05 SAST ]]> Finite precision arithmetic in Polyphase Filterbank implementations http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38503 Wed 12 May 2021 23:20:29 SAST ]]> Oblique incidence investigations of the ionosphere over the Southern Ocean http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5438 Wed 12 May 2021 23:11:44 SAST ]]> Towards modelling the formation of ore bodies initial results dealing with the fluid mechanical aspects of magma chamber convection http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5492 Wed 12 May 2021 23:08:31 SAST ]]> An investigation into improved ionospheric F1 layer predictions over Grahamstown, South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5511 Wed 12 May 2021 22:45:13 SAST ]]> Thermoluminescence of secondary glow peaks in carbon-doped aluminium oxide http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5537 Wed 12 May 2021 22:37:25 SAST ]]> Comparison of A₄ neutrino mass models http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5554 Wed 12 May 2021 22:30:24 SAST ]]> Analysing emergent time within an isolated Universe through the application of interactions in the conditional probability approach http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38547 Wed 12 May 2021 20:57:26 SAST ]]> The 2326 MHZ radio continuum emission of the milky way http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5450 Wed 12 May 2021 20:17:57 SAST ]]> An analysis of ionospheric response to geomagnetic disturbances over South Africa and Antarctica http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5534 Wed 12 May 2021 20:15:43 SAST ]]> Nonlinear optical responses of phthalocyanines in the presence of nanomaterials or when embedded in polymeric materials http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:25548 Wed 12 May 2021 20:07:23 SAST ]]> The photo-fluorescence properties of some organic materials http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5514 Wed 12 May 2021 20:04:33 SAST ]]> Observations of diffuse radio emission in the Perseus Galaxy Cluster http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38233 Wed 12 May 2021 19:59:26 SAST ]]> First H F Doppler soundings of the ionosphere at SANAE http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5500 Wed 12 May 2021 19:56:40 SAST ]]> Thermoluminescence of annealed synthetic quartz http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:19957 Wed 12 May 2021 19:55:06 SAST ]]> Expanding the capabilities of the DPS lonosonde system http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5560 Wed 12 May 2021 19:50:08 SAST ]]> Assignment of spin and parity to states in the nucleus ¹⁹⁶T1 http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5558 Wed 12 May 2021 19:49:57 SAST ]]> Tomographic imaging of East African equatorial ionosphere and study of equatorial plasma bubbles http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:28516 Wed 12 May 2021 19:46:51 SAST ]]> Third generation calibrations for Meerkat Observation of Saraswati Supercluster http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:65374 Wed 10 Jan 2024 11:01:27 SAST ]]> The effects of particle precipitation on the ionosphere in the South Atlantic Anomaly Region http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5463 Tue 31 Aug 2021 10:06:57 SAST ]]> Predictability of Geomagnetically Induced Currents using neural networks http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5483 Thu 26 Aug 2021 14:37:41 SAST ]]> On the gravitational dual to strongly coupled fluids http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:45280 Thu 23 Jun 2022 12:03:49 SAST ]]> The EPR paradox: back from the future http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:20338 Thu 23 Jun 2022 11:24:04 SAST ]]> Dynamics of stimulated luminescence in natural quartz: Thermoluminescence and phototransferred thermoluminescence http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38509 Thu 13 May 2021 15:55:13 SAST ]]> CubiCal: a fast radio interferometric calibration suite exploiting complex optimisation http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:30711 Thu 13 May 2021 15:04:39 SAST ]]> The implementation of a core architecture for geophysical data acquisition http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5471 Thu 13 May 2021 13:16:36 SAST ]]> Development of a neural network based model for predicting the occurrence of spread F within the Brazilian sector http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5460 Thu 13 May 2021 09:13:17 SAST ]]> Structure of the nucleus ¹¹⁴Sn using gamma-ray coincidence data http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5562 Thu 13 May 2021 08:52:22 SAST ]]> A VLBI polarisation study of 43 GHZ SiO masers towards VY CMA http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5498 Thu 13 May 2021 08:22:08 SAST ]]> Investigation into the extended capabilities of the new DPS-4D ionosonde http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5472 Thu 13 May 2021 08:08:05 SAST ]]> A new empirical model for the peak ionospheric electron density using neural networks http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5478 Thu 13 May 2021 07:39:27 SAST ]]> Measuring the RFI environment of the South African SKA site http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5474 Thu 13 May 2021 07:16:45 SAST ]]> Designing and implementing a new pulsar timer for the Hartebeesthoek Radio Astronomy Observatory http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5458 Thu 13 May 2021 07:10:11 SAST ]]> Long-term analysis of ionospheric response during geomagnetic storms in mid, low and equatorial latitudes http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:28517 Thu 13 May 2021 07:06:25 SAST ]]> Calibration and interpretation of A 2.3 GHz continuum survey http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5502 L > -58° is studied. It is dominated by a plateau of emission for L < -26°. This is interpreted as a combination of thermal and nonthermal radiation emitted by a ring of gas symmetric about the galactic centre with a radius of 4 - 6 kpc.]]> Thu 13 May 2021 06:53:12 SAST ]]> The effect of different parameters on the rupture properties of leather in a tensile test http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5462 Thu 13 May 2021 06:48:58 SAST ]]> Aspects of the symplectic and metric geometry of classical and quantum physics http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5452 Thu 13 May 2021 06:28:45 SAST ]]> Studies in ionospheric ray tracing http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5501 Thu 13 May 2021 06:28:30 SAST ]]> A VLBI study of OH masers in a proto-planetary nebula OH 0.9+1.3 http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5499 Thu 13 May 2021 06:26:01 SAST ]]> Multi-instrument observations of ionospheric irregularities over South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5476 Thu 13 May 2021 06:18:50 SAST ]]> Observations of glitches in PSR 0833-45 and 1641-45 http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5480 Thu 13 May 2021 06:12:50 SAST ]]> Real-time audio spectrum analyser research, design, development and implementation using the 32 bit ARMR Cortex-M4 microcontroller http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:25997 Thu 13 May 2021 06:12:17 SAST ]]> TiRiFiG, a graphical 3D kinematic modelling tool http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:30558 Thu 13 May 2021 06:10:31 SAST ]]> Link between ghost artefacts, source suppression and incomplete calibration sky models http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5556 Thu 13 May 2021 06:07:57 SAST ]]> A Bayesian approach to tilted-ring modelling of galaxies http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38466 Thu 13 May 2021 05:58:42 SAST ]]> Solar cycle effects on GNSS-derived ionospheric total electron content observed over Southern Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5489 Thu 13 May 2021 05:54:01 SAST ]]> Progress towards the development and implementation of an unambiguous copper wire fingerprinting system http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5484 Thu 13 May 2021 05:52:34 SAST ]]> Observing cosmic reionization with PAPER: polarized foreground simulations and all sky images http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:29218 0.3 h Mpc -¹ We also analyzed data from the last observing season of PAPER via all-sky imaging with a view to characterize the foregrounds. We generated an all-sky catalogue of 88 sources down to a flux density of 5 Jy. Moreover, we measured both polarized point source and the Galactic diffuse emission, and used these measurements to constrain our model of polarization leakage. We find the leakage due to a population of point sources to be 12% lower than the prediction from our polarized model.]]> Thu 13 May 2021 05:43:39 SAST ]]> Observations of diffuse radio emission in the Abell 773 galaxy cluster http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38394 Thu 13 May 2021 05:41:52 SAST ]]> MEQSILHOUETTE: a mm-VLBI observation and signal corruption simulator http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:25019 Thu 13 May 2021 05:32:08 SAST ]]> Modelling and investigating primary beam effects of reflector antenna arrays http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38635 Thu 13 May 2021 05:23:36 SAST ]]> Thermoluminescence of natural quartz http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5543 Thu 13 May 2021 05:21:09 SAST ]]> The SKA's the limit : on the nature of faint radio sources http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5504 Thu 13 May 2021 05:20:46 SAST ]]> A neural network based ionospheric model for the bottomside electron density profile over Grahamstown, South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5477 Thu 13 May 2021 05:19:34 SAST ]]> Optimizing MIDAS III over South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5517 Thu 13 May 2021 05:10:35 SAST ]]> The observation of extended sources with the Hartebeesthoek radio telescope http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5479 Thu 13 May 2021 05:09:50 SAST ]]> A pilot wide-field VLBI survey of the GOODS-North field http://vital.seals.ac.za:8080/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 ]]> Empirical modelling of the solar wind influence on Pc3 pulsation activity http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5464 Thu 13 May 2021 05:04:36 SAST ]]> Properties of traveling ionospheric disturbances (TIDs) over the Western Cape, South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5557 Thu 13 May 2021 04:57:39 SAST ]]> Machine learning methods for calibrating radio interferometric data http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:31398 Thu 13 May 2021 04:55:12 SAST ]]> The establishment of a Lidar facility at Rhodes University http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5445 Thu 13 May 2021 04:52:35 SAST ]]> Calibration and imaging with variable radio sources http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:24721 Thu 13 May 2021 04:51:42 SAST ]]> The search for an ionospheric model suitable for real-time applications in HF radio communications http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5488 Thu 13 May 2021 04:41:21 SAST ]]> A 150 MHz all sky survey with the Precision Array to Probe the Epoch of Reionization http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:34556 Thu 13 May 2021 04:40:36 SAST ]]> Physics and applications of scintillation detectors http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5482 Thu 13 May 2021 04:31:15 SAST ]]> Finite element modelling of magma convection and attendant groundwater flow http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5467 Thu 13 May 2021 04:24:15 SAST ]]> The development of an improved coded-pulse, vertical-incidence ionosonde http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5436 Thu 13 May 2021 03:43:09 SAST ]]> Distributed control applications using local area networks: a LAN based power control system at Rhodes University http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5461 Thu 13 May 2021 03:37:19 SAST ]]> Advanced ionospheric chirpsounding http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5446 Thu 13 May 2021 03:33:12 SAST ]]> Thermoluminescence and phototransferred phermoluminescence of synthetic quartz http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:38472 Thu 13 May 2021 03:05:20 SAST ]]> Modelling Ionospheric vertical drifts over the African low latitude region http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:28396 Thu 13 May 2021 02:06:20 SAST ]]> Foreground simulations for observations of the global 21-cm signal http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:30557 Thu 13 May 2021 01:46:55 SAST ]]> Beta decay of 100/400 Zr produced in neutron-induced fission of natural uranium http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:20353 Thu 13 May 2021 01:43:27 SAST ]]> A light-emitting-diode pulsing system for measurement of time-resolved luminescence http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:20976 Thu 13 May 2021 01:37:18 SAST ]]> Geomagnetically induced current characteristics in southern Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5469 Thu 13 May 2021 01:31:54 SAST ]]> Advanced radio interferometric simulation and data reduction techniques http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:26875 Thu 13 May 2021 01:03:59 SAST ]]> A global ionospheric F2 region peak electron density model using neural networks and extended geophysically relevant inputs http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5470 Thu 13 May 2021 00:53:58 SAST ]]> Computer control of an HF chirp radar http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5455 Thu 13 May 2021 00:45:07 SAST ]]> A contribution to TEC modelling over Southern Africa using GPS data http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5456 Thu 13 May 2021 00:26:54 SAST ]]> Forecasting solar cycle 24 using neural networks http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5468 Thu 13 May 2021 00:24:49 SAST ]]> Variability analysis of a sample of potential southern calibration sources http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5495 Thu 13 May 2021 00:13:28 SAST ]]> Single station TEC modelling during storm conditions http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:20545 Thu 13 May 2021 00:00:25 SAST ]]> Accelerated implementations of the RIME for DDE calibration and source modelling http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:42199 Thu 13 Jul 2023 12:40:08 SAST ]]> Semantic segmentation of astronomical radio images: a computer vision approach http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:71937 Thu 04 Apr 2024 19:33:11 SAST ]]> MeerKAT observations of three high-redshift galaxy clusters http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:71936 6×1014 M⊙ at intermediate redshifts (0.3 < z < 0.4), providing support to their connection between mergers, which provide the necessary energy to re-accelerate particles via turbulence. Probing the redshift evolution of radio halos is an important test of the turbulent re-acceleration scenario, as fewer halos are expected at high redshift, given the same mass interval. In this thesis, we present MeerKAT observations at 1.28 GHz of three high-redshift (PSZ2G254.08- 58.45, PSZ2G255.60-46.18 and PSZ2G277.76-51.74, in the 0.42 ≲ z ≲ 0.46 range) clusters, with masses M500 ≳ 6.2 × 1014 M⊙, selected for their disturbed dynamical state – inferred from existing X-ray observations. Our observations reached rms noise values between 20 and 23.5 μJy beam−1, with ∼ 4′′ angular resolution. No evidence of diffuse emission is found at ii full resolution. Low-resolution (∼ 30′′) images achieved rms noise levels of 30-50 μJy beam−1, amongst the deepest observations of high-redshift targets. One radio halo was detected in the least massive cluster PSZ2G254.08-58.45 extending over ∼ 500 kpc, with a 1.20 } 0.08 mJy integrated flux density. We placed a ∼1 mJy upper limit at 95% confidence level on the radio halo flux density for the other two targets. The radio-halo detection is consistent with the recent P1.4 GHz − M500 correlation from Cuciti et al. (2021b), while the upper limit on PSZ2G255.60-46.18 is consistent with being on the correlation. On the other hand, the upper limit on PSZ2G277.76-51.74 places the radio halo well below the correlation. Recently a 1.5 GHz survey (Giovannini et al., 2020) detected a slightly higher fraction of radio halos in clusters in the same redshift range, with power and size typically higher than what we found in our observations. Both observations are, however, not inconsistent with each other. Our results, although with limited statistics, do not disfavour the current scenario of radiohalo formation based on the turbulent re-acceleration model.]]> Thu 04 Apr 2024 19:25:15 SAST ]]> M3: Mining Mini-Halos with MeerKAT http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:72181 Sun 21 Apr 2024 13:42:47 SAST ]]> An investigation of traveling ionospheric disturbances (TIDs) in the SANAE HF radar data http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:49986 Sun 09 Oct 2022 17:48:47 SAST ]]> A statistical study of travelling ionospheric disturbances over the African-European and American sectors http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:71956 4 and Dst_ -50 nT was used as a criterion for geomagnetic disturbed conditions, while the four geomagnetically quiet days were selected each month based on Kp < 3. Observations of TIDs are made using Global Navigational Satellite Systems (GNSS) total electron content derived data. During quiet conditions, seven and two transhemispheric TIDs were identified over the African-European and American sectors, respectively. The observed TIDs originated from the wintertime hemisphere and propagated into the summertime hemisphere. The horizontal velocity, periods, and horizontal wavelengths of TIDs are in range of cH = 120-274 m/s, 48-80 min and _H = 379-1104 km, respectively. These quiet-time equatorward TIDs have been associated with tertiary gravity waves (GWs) from the dissipation of secondary GWs which are in turn generated from the dissipation of mountain waves (MWs) as a result of excited orographic forcing. The poleward TIDs during geomagnetically quiet conditions over the African and American sectors occur mainly during local daytime. Poleward TIDs were observed mostly in the African-European sector than the American sector. Their horizontal propagation velocities and periods range between 129-280 m/s and 39-70 min over African-European and American sectors. Although the mechanisms responsible for launching quiet-time poleward TIDs have not been established in this study, lower atmospheric processes such as convection systems, sudden stratospheric warming and cold weather fronts may have a role in their generation. During geomagnetic storms in the African sector, almost all poleward TIDs (with the exception of two cases) during the main phase were large-scale with horizontal velocities and periods ranging from 250-503 m/s and 30 min to 2 hours. During recovery phase, poleward TIDs fall under the category of medium scale. In the American sector, the majority of poleward TIDs occurred during the storm's main phase, as opposed to the African-European sector, which experienced a significant number of poleward TIDs during the recovery phase. The periods and horizontal velocities of TIDs range from 45 min-1.5 h and 180-296 m/s during main phase. During the recovery phase, the horizontal velocity and period range from 177-271 m/s and 40-1.5 h, respectively. Overall, it has been shown that statistically, changes in equatorial electrodynamics related to enhanced eastward electric _eld and hence increased equatorial electrojet (vertical E_B drift) correlates highly with the reported poleward TIDs.]]> Sat 06 Apr 2024 13:06:52 SAST ]]> The development of an ionospheric storm-time index for the South African region http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:42937 4. The modeling methods used in the study were artificial neural network (ANN), linear regression (LR) and polynomial functions. The approach taken was to first test the modeling techniques on a single station before expanding the study to cover the regional aspect. The single station modeling was developed based on ionosonde data over Grahamstown. The inputs for the model which related to seasonal variation, diurnal variation, geomagnetic activity and solar activity were considered. For the geomagnetic activity, three indices namely; the symmetric disturbance in the horizontal component of the Earth’s magnetic field (SYM − H), the Auroral Electrojet (AE) index and local geomagnetic index A, were included as inputs. The performance of a single station model revealed that, of the three geomagnetic indices, SYM − H index has the largest contribution of 41% and 54% based on ANN and LR techniques respectively. The average correlation coefficients (R) for both ANN and LR models was 0.8, when validated during the selected storms falling within the period of model development. When validated using storms that fall outside the period of model development, the model gave R values of 0.6 and 0.5 for ANN and LR respectively. In addition, the GPS total electron content (TEC) derived measurements were used to estimate foF2 data. This is because there are more GPS receivers than ionosonde locations and the utilisation of this data increases the spatial coverage of the regional model. The estimation of foF2 from GPS TEC was done at GPS-ionosonde co-locations using polynomial functions. The average R values of 0.69 and 0.65 were obtained between actual and derived _foF2 over the co-locations and other GPS stations respectively. Validation of GPS TEC derived foF2 with RO data over regions out of ionospheric pierce points coverage with respect to ionosonde locations gave R greater than 0.9 for the selected storm period of 4-8 August 2011. The regional storm-time model was then developed based on the ANN technique using the four South African ionosonde stations. The maximum and minimum R values of 0.6 and 0.5 were obtained over ionosonde and GPS locations respectively. This model forms the basis towards the regional ionospheric storm-time index.]]> Mon 31 May 2021 15:12:57 SAST ]]> Dynamics of charge movement in ∞-Al2O3:C,Mg using thermoluminescence phototransferred and optically stimulated luminescence http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:57237 Mon 24 Oct 2022 14:52:01 SAST ]]> Night-time gravity waves detected with multi-frequency airglow imager http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:42931 Mon 17 May 2021 13:00:31 SAST ]]> Neutral Atomic Hydrogen in Gravitationally Lensed Systems http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:45263 Mon 15 Nov 2021 14:52:54 SAST ]]> Neutral winds and tides over South Africa http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:49993 Mon 10 Oct 2022 08:47:40 SAST ]]> Behaviour of quiet time ionospheric disturbances at African equatorial and midlatitude regions http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:28228 Fri 17 Sep 2021 14:51:46 SAST ]]> Data compression, field of interest shaping and fast algorithms for direction-dependent deconvolution in radio interferometry http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:21089 Fri 07 Jul 2023 06:30:13 SAST ]]>