Electrodynamic drift in the nocturnal F-region ionosphere caused by conjugate point sunrise

A rapid change in the electrical conductivity of the ionosphere occurs at the time of sunrise. When the conjugate point is in darkness, this change causes a change in the component of the dynamo electrostatic field normal to the sunrise line. This change in electrostatic field should cause a corresponding change in the vertical component of ion drift velocities in the F-region. The theory we develop predicts changes in ion drift velocities that are of the same order of magnitude, tens of meters per second, as the dynamo region winds. The effect may be detectable as an upward or downward movement of the nocturnal ionosphere at the time of conjugate point sunrise.