SporadicEand the wind structure of theEregion

Observations of neutral winds from visible trails of gun-launched vehicles and radio soundings of the ionospheric sporadic E layers are described and compared. It is shown that the wind structure accounts for many features of the sporadic E layer variation on two nights of observation, through the vertical ion convergence mechanism described most recently by MacLeod [1966]. Except for some transient disagreements, the sporadic E is found to accompany the height variation of certain levels of zero ion velocity induced by the neutral wind. The peak electron number density of the layers diminishes when the wind structure leads to ion divergence at the sporadic E height, and the density is observed to increase when the ion velocity permits the descent of ‘new’ ionization from above. New layers ‘arrive’ at night in accord with the observed development and descent of new nodes of ion convergence. The daytime evolution of a principal sporadic E layer is described and related to its subsequent nighttime association with the wind structure. Together with other published evidence that similar layers consist of long-lived monatomic ions ultimately from meteoric influx, it is concluded that the neutral wind serves as a scavenger of this material that would otherwise accumulate to a far higher ionic concentration in the upper atmosphere.