摘要: We derive a stability criterion for the large-scale structuring of ionospheric plasma clouds due to E × B gradient drift instability. For equilibrium we consider cylindrical two-dimensional water bag cloud aligned along uniform magnetic field that is polarized by neutral wind. perform analysis allows three-dimensional perturbations (in r, θ, and z), both local global modes. find when parallel wave number kz exceeds threshold value, exponentially growing poloidal eigenmodes form which are localized on “backside” cloud. This in contrast = 0 limit there no exponential solutions. As increased further, unstable modes localize at finite angle away from backside, point where diamagnetic propagation velocity Vd balances convective flow background around cloud, Vb. instability stable > Vb so longer susceptible structuring. apply these results barium estimate they will cease L⊥ < (cT/eB)(M + 2)/2Vn transverse size T Te Ti total temperature, M nc/nb (nc density, nb density), Vn wind velocity. mid-latitude releases ∼180 km ∼ 160–480 m, consistent with observations.