Abstract
To enhance the quality and near real time production of K-based planetary magnetic activity indices, such as am, and longitude-sector indices, aλ, there is a requirement for local three-hourly K index values from the South Atlantic observatory at Port Stanley. We describe the computer algorithm used to estimate the solar regular variation, SR, and techniques used to establish the parameters required to derive the K indices. We analyse the results by comparing the distributions of K values with observatories at similar geomagnetic latitude and thus with likely similar levels of geomagnetic activity. We also look for biases by comparing the indices directly to those from nearby observatories. Both sets of results show a good overall agreement. However adjustment of input parameters will be necessary if improved agreement with the indices from the other observatories is required.