Possible mechanism for the formation of negative ions in the upper part of the ionospheric D-region

Laboratory studies involving the bombardment of ice with fast electrons (Avdiev et al., 1983) have led to a new mechanism for the formation of negative ions in the upper D-region. According to this mechanism, negative ions can arise when energetic electrons precipitate in the upper atmosphere in the presence of a sufficient quantity of ice crystals; this can occur during auroral absorption in the mesopause at high latitudes where noctilucent clouds presumably consisting of ice particles are present. It is concluded that the proposed mechanism makes it possible to explain the presence of heavy negative ions at heights above 80 km, and to interpret measured mass spectra in a new way.