Electron Densities Below 100 Kilometers at Midlatitudes (L = 2.5–4.0) During Solar Minimum and Maximum Years: Preliminary Model Calculations

Abstract

Electron production rates due to photoionization, qs(χ, h), and particle precipitation, qp(h), have been calculated for the midlatitude ionosphere from 70 to 140 km for conditions typical of solar minimum and maximum years. A simple model in which E and D regions are defined by Lyman β, EUV (30–120 A), Lyman α, and X rays (2–10 A) is used. An atmospheric model having annual variations for the major constituents and a seasonally constant profile of nitric oxide is also incorporated in the calculations. Electron density profiles have been derived using recent estimates of αeff. Results of calculations are shown for solar zenith angles χ = 37° and 72°, typical of noon values for summer and winter seasons. Fluxes of precipitated electrons typical of geomagnetic midlatitudes (L = 2.5–3.5) are used. For both solar minimum and maximum years, the seasonal variations in qt(h) and Nt(h) differ significantly from those of a Chapman layer, partly because production rates from 80 to 100 km due to particle precipitation are from 25 to 90% of the total. One aspect of the ‘heavily ionized’ winter lower ionosphere is discussed. Calculated diurnal variations in ionization for conditions typical of solar maximum years at higher latitudes (L = 3.5–4.0) also reveal irregular variations with χ due to the particle precipitation contribution.