Combined view of in situ ion/electron plasma density in the European/African longitudinal sector at 20–21 UT on 23 April 2023. (a) Geographical location of satellite overpasses: Swarm B and two COSMIC-2 C2E2 and C2E4. The thick black line marks the magnetic equator, the thin gray lines are magnetic field lines, the shaded area shows nighttime. The arrows point towards the conjugate points from the midlatitude irregularities detected by Swarm B. (b) Corresponding in situ electron density (Ne) variations along the Swarm B pass (20.32–20.67 UT) plotted as a function of geographical latitude. (c) Corresponding in situ ion density (Ni) variations along COSMIC-2 C2E2 and C2E4 passes (20.68–20.98 UT and 20.30–20.62 UT, respectively) plotted as a function of geographical longitude.