Molecular ion upflow in the cleft ion fountain

Although the ionosphere is a continuous emitter of escaping light ions (H+ and He+) and in the auroral zone a continuous emitter of escaping heavy atomic ions (O+ and N+), it only sporadically emits molecular ions. This is due to the significant gravitation barrier to their outflow and to the chemical barrier created by their short life times against loss to dissociative recombination in the F region. The outflow of molecular ions requires a special set of circumstances. In this paper we present evidence that one ingredient for those special circumstances is the presence, in the ionosphere, of a strong convection electric field. This can occur in various places near the auroral zone, in nightside subauroral ion drift events, and in the cusp. We show several examples of Dynamics Explorer (DE) 1 and 2 near‐conjunction data in which molecular ions are seen at high altitude (1400–4000 km) by DE 1 near where DE 2 sees strong cusp associated plasma convection and ionospheric and thermospheric modification.