Why Transequatorial propagation depends on the equatorial ionization anomaly, two dense crests of F-region ionization that form on either side of the magnetic equator as daytime ionization is lifted and redistributed by the equatorial fountain effect. Those crests take hours to build, so they reach maximum density late in the day, and signals ricochet between them in the afternoon and early evening. TE paths run roughly north-south across the magnetic equator and often support frequencies well above the normal MUF, sometimes into the VHF range.