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Abstract
Particles of dust (of cosmic origin, for example) falling through a supersaturated layer near the mesopause will become coated with ice. The thickness of this coating is an important parameter in discussing the optical properties and mass budget of the system. Calculations of this thickness are presented, including the dependence on the vertical extent of the layer, the humidity, the vertical wind velocity and the density of the dust particles. The results of these calculations indicate the range of conditions that might be sufficient to produce a noctilucent cloud. The effects of sedimentation on the mass budget are considered with the conclusion that an updraft of tens of cm/sec is necessary for a steady-state condition.DOI: 10.1111/j.2153-3490.1966.tb00257.x