The effective recombination coefficient of electrons in the ionosphere between 50 and 150 km

The literature on values of the effective recombination coefficient α of electrons between heights of 50 and 150 km has been critically examined. It is found that, during auroral events at night, it may be represented by the expression α = 4.30×10 −6 exp (−2.42×10 −2 h) + 8.16×10 12 exp(−0.524 h), where α is in cm −3 s −1 and h is in kilometers. During a wide variety of phenomena, including polar cap absorption, sudden phase anomalies, solar proton events and solar flares, the expressions α = 652 exp(−0.234 h) (night) and α = 0.501 exp(−0.165 h) (day) are reasonably representative between 50 and 100 km. No values are available above 100 km. The above values are certainly not reliable to within a factor of 2, and in some cases not even to within an order of magnitude.