双离子成分下的赤道电离层R-T不稳定性

等离子体R-T(Rayleigh-Taylor)不稳定性被认为是赤道夜间F区电离层产生不规则体的主要机制, 经典理论中只考虑了氧离子一种正离子成分, 等离子体R-T不稳定性的表达式与氧离子质量和密度无关. 事实上, 在有些情况下, 电离层F区往往不仅仅只有一种正离子存在. 本文利用连续性方程、动量方程和电流守恒方程, 采用微扰方法, 推导了双离子成分条件下, 赤道电离层R-T不稳定性线性增长率的表达式, 研究多种正离子成分对R-T不稳定性的影响. 结果表明, 双离子成分下线性增长率与两种正离子的数密度和质量都相关, 增长率的大小依赖于两种正离子成分所占的比例. 

Equatorial Ionosphere Rayleigh-Taylor Instability in the Presence of Double-ion Species

Plasma Rayleigh-Taylor instability plays a crucial role in the development of irregularities in the nocturnal equatorial ionosphere. In traditional theories, only the dominant element O+ is taken into consideration. As a result, the liner equation is independent with the ion mass and density. In fact, in some cases, there are not only one kind of positive ion in the F region of the ionosphere, such as in dusty plasma or in the ionospheric disturbances resulting from artificially chemical releases. It is essential to understand the effect of molecular ions in the collisional Rayleigh-Taylor instability. In this paper, a linear perturbation analysis associated with continuity equations, momentum equations and current conservation equation has been used to obtain a growth rate expression in the presence of double-ion species. The new expression reveals that the growth rate is dependent with the number densities and masses of both the ion elements, and especially, the proportions of the two kinds of ions contribute to growth rate.