Fig. 3

The SAO Explorer profilogram plot of the electron density profiles at Millstone Hill, Massachusetts for 6–8 November 2004 shows the timeline of ionospheric response to an intense interplanetary shock event on 7 November 18:27 UT (dashed vertical line). Colors indicate the plasma density, and the black line marks the peak height h_mF₂. Shortly after the shock event, the F₂ layer rose sharply in comparison to the previous day baseline. During the night on November 8 a severe 8-hour absorption event blinded the instrument, while the densities during the daytime are markedly low (Zong et al., 2010).