Figure 5From: Filtering ionosphere parameters to detect trends linked to anthropogenic effectsTrend of foF2 measured at Juliusruh. foF2 residuals obtained using only years around solar activity (a) minimum periods and (b) maximum periods, filtering solar activity with F10.7. Linear trends (dashed line) are -4 × 10-3 MHz/year in (a) and -5 × 10-3 MHz/year in (b).Back to article page