Ascension and Port Stanley geomagnetic observatories and monitoring the South Atlantic Anomaly

Our 15-year experience of operating two remote observatories, Ascension and Port Stanley, in the south Atlanticis described. These observatories help monitor the South Atlantic Anomaly (SAA), a region of weak magneticfield which causes considerable problems for spacecraft operators. One-minute and one-second values fromthese observatories, and other observatories both inside and outside the SAA, are analysed. We investigatewhether the SAA, and its growth over time, are having any tangible effect on the observed external field variations.Whilst only able to illustrate the long-term characteristics of the irregular external field related to the solarcycle and not due to any long-term changes in the internal field, we do isolate micropulsation signals at sitesinside the SAA which contain more power than at sites outside