Latitudinal variation of total electron content in the winter at middle latitudes

Studies of total electron content (TEC) have been made by using data obtained during three winter solstices in Paris, France, and Kiruna, Sweden. A nocturnal winter maximum is clearly shown by these data, and an effort is made to hypothesize its cause. A two-fold hypothesis is offered; the increase in TEC is attributed to an electron flux descending from the protonosphere. This flux is linked to lowering electron temperatures in the force tube after sunset in the conjugate hemisphere. In addition to this production process, a regulatory process is invoked to reconcile the observed values with the maximum flux intensity compatible with the theory. The regulatory process is attributed to an interaction between the neutral winds and the ionospheric plasma in the presence of the earth's magnetic field.