Geomagnetic observations on Tristan da Cunha, South Atlantic Ocean

Few geomagnetic ground observations exist of the Earth’s strongest core field anomaly, the South Atlantic Anomaly(SAA). The geomagnetic repeat station on the island Tristan da Cunha, located half-way between South Africaand South America at 37° 05’ S, 12° 18’ W, is therefore of crucial importance. We have conducted several sets ofrepeat station measurements during magnetically quiet conditions (Kp 2o or less) in 2004. The procedures are describedand the results are compared to those from earlier campaigns and to the predictions of various global fieldmodels. Features of the local crustal bias field and the solar quiet daily variation are discussed. We also evaluatethe benefit of continuous magnetic field recordings from Tristan da Cunha, and argue that such a data set is a veryvaluable addition to geomagnetic satellite data. Recently, funds were set up to establish and operate a magnetometerstation on Tristan da Cunha during the Swarm magnetic satellite mission (2011-2014)