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Figure 3

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Yearly averages of TEC [TECU], NmF2 [1010 m−3], foF2 [0.1 MHz], τ [km] and hmF2 [km] at noon in comparison with the solar F10.7 index [sfu] for selected ionosonde stations in the years 1996–2022 for Juliusruh, 2000–2022 for Boulder (2003 interpolated) and 2002–2022 for Kokubunji. Corresponding linear regression lines are dashed. The right upper panel shows the relationship between observed TEC, foF2, and F10.7.

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