Key ionospheric characteristics measured at Dourbes during the eclipse day, 20 March 2015 (A, C, E, G) and the reference day, 21 March 2015 (B, D, F, H). GPS TEC (A, B); f _o F₂, f _o F₁ and f _o E (C and D); h′F₂ and h′E (E and F) and slab thickness (G and H). Instantaneous measurements denoted with dots, the 27-day medians (based on data from 4 to 30 March) plotted with solid (grey) curves, and the (approximated) daytime trends are plotted with dashed lines. The time period of the eclipse is shaded and all measurements during that time frame are highlighted with solid black curves (7-point running average). Red arrows indicate the maximum deviation (from medians) during the eclipse.