Within the Inkaba yeAfrica project, the number of geomagnetic repeat stations surveyed in southern Africa has been increased recently from eight to almost 40, through cooperation between Hermanus Magnetic Observatory (HMO), South Africa and GeoForschungsZentrum Potsdam (GFZ), Germany. Taking advantage of the extensive network of well-marked repeat stations formerly established by HMO in South Africa, Namibia and Botswana, and experience gained in using on-site variometers in former repeat station surveys carried out by GFZ, we could significantly improve the spatial data coverage of the area and also the quality of the results. Here we report on the survey and data processing methods, and discuss the accuracy of results, particularly with respect to the ability of the data to reflect the undisturbed internal magnetic field. Moreover, we briefly discuss how differences in the variometer recordings can reflect possible lateral changes in lithospheric conductivity.
The validation of the Local Disturbance index (LDi) and its first time derivative Local Current index (LCi) is performed in the Southern Hemisphere. Two South African magnetic observatories, Hermanus and Hartebeesthoek contributed data for this study, and two South African power stations, Grassridge and Matimba, provided geomagnetically induced current (GIC) data. This validation focused on two major geomagnetic storms, Halloween and Saint Patrick's Day events that occurred in October 2003 and March 2015, respectively. The comparative evaluation of the LDi and LCi indices was executed with the help of the local horizontal component (H) and also comparing them to the global index SYM‐H. A direct comparison to measured GIC shows that LCi performs slightly better than dH/dt as a proxy for GIC. The comparison of the LDi 1‐hr magnetic disturbances values to ones calculated applying a Linear phase Robust Non‐Smoothing method to the H component yields a Pearson correlation coefficient R greater than 0.960 for different groups of magnetic storms based on intensity. The estimated SYM‐H index from LDi data showed a possible difference of about 300 nT from the published SYM‐H index values around 20:00 UT on 29 October 2003, during the Halloween storm. This study has shown that the LDi and LCi indices, developed in the Northern Hemisphere, can be calculated at similar latitudes in the Southern Hemisphere for studying local space weather conditions and now‐casting successfully local geomagnetic events.
Polynomial surface modelling is one of several useful methods to represent the geomagnetic field over a restricted area. This technique was applied to CHAMP satellite data for the period 2001-2005 to investigate rapid secular variation fluctuations at 400 km altitude over southern Africa region between 10• and 40• South in latitude and between 10• and 40
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.