Some winter characteristics of the northern high-latitude ionosphere

Langmuir probe measurements of the winter diurnal behavior of the electron density (Ne) and temperature (Te) at 1000 km at high latitudes are presented. The data are represented by contour plots of Ne and Te on a grid of geomagnetic latitude and local time. The time period studied is November 1, 1965, through February 12, 1966. The Ne distribution is characterized by a zonal structure where the auroral oval is the transition region between the midlatitude and polar zones. Ne in the midlatitude zone exhibits a quasi-steady state through most of the night, and both Ne and Te increase in value to an afternoon maximum. Ne in the dark polar zone decays until midnight after which the ionization increases toward a daytime level. The transition region, represented by the oval, shows enhancements in Ne suggestive of particle flux sources. In general, the dayside Te contours do not correlate with the Ne contours. Limited comparisons between winter and summer indicate strong seasonal effects in the Ne pattern and unusually large values of Te in the winter midlatitude zone. Characteristic troughs in Ne appear on the nightside for both seasons. Possible ionization sources that would be consistent with the observed ionization patterns are considered.