Dissociation, recombination and attachment processes in the upper atmosphere II. The rate of recombination

Abstract The ionized regions of the upper atmosphere include, not only neutral atoms and molecules, electrons and positive ions, but also negative ions. Of these, electrons are alone effective in producing reflexion of wireless waves; so that an electron attached to a neutral molecule to form a negative ion is as effectively removed from active participation in these phenomena as one recombined with a positive ion to form a neutral molecule. The decay of electron density at night has been attributed by some authors to recombination with positive.ions and by others to attachment by neutral molecules. The first process is in agreement with the observed law of decay and has the additional advantage of making it easily possible to understand the formation of layers of concentrated ionization; on the other hand, the chance of attachment to a molecule per impact would have to be extremely small for the attachment rate to be negligible, since the number of collisions per second with neutral atoms is very much greater than with positive ions.