On unequal distributions of positive and negative ions in the upper stratosphere

In the middle atmosphere below about 60 km, ionizations are produced by cosmic rays. Electrons produced in this ionization process get immediately attached with O-2. O-2(-) thus formed are then quickly converted into the stable negative ions. This makes the number of positive ions in this region equal to the number of negative ions. However, the results of a partial reflection experiment at Scott Base, Antartica show, very often, the presence of an ionization layer between 40 and 55 km. In such condition, at 45 km, an electron number density about 1000 cm(-3) has been reported. A chemical scheme in which both positive and negative ion reactions are considered, has been used to explain this feature. We have studied the effect of changes of temperature and all the minor constituents relavent to the ions in this region. It appears that a reasonable increase in electron - ion production rate and a simultaneous increase in the detachment rate of electrons from negative ions can explain this feature.