Fig. 9From: Morphology of the southern African geomagnetic field derived from observatory and repeat station survey observations: 2005–2014Secular variation of D, H, and Z components at Tsumeb observatory as a function of time between 2005 and 2014. The black dots show monthly mean secular variation estimates derived as running annual differences. The CHAOS-5 (black line) and SAREG (brown dashed line) models are included. Piecewise linear fits to the data provide estimates of secular acceleration as given in the legendsBack to article page