Effects of molecular ions on the Rayleigh-Taylor instability in the night-time equatorial ionosphere

In view of composition measurements in the night-time equatorial ionosphere , the role of molecular ions on the collisional Rayleigh-Taylor instability is examined using a linear perturbation analysis and a growth rate express ion in the presence of double-ion species is obtained. The expression revea ls that the growth rate depends on the number densities of both the ion spe cies. This is in contrast to a single ionic constituent wherein the growth rate is independent of number density. The numerical calculation under real istic conditions reveals that the growth rate of the instability reduces wi th the introduction of the second dominant ion species and never exceeds th e growth rate corresponding to a single ionic constituent. Further, the gro wth of the plasma instability is feasible even when the scale length of the second dominant ion is negative. (C) 1999 Elsevier Science Ltd. All rights reserved.