The flux and spatial distribution of micrometeoroids in the near-Earth environment

The near-Earth micrometeoroid data of Prospero has been re-appraised in the light of recent data from the HEOS satellite and other detectors which sampled the near-Earth region. This has enabled a cumulative micrometeoroid flux-mass curve to be defined for this region which shows a pronounced flux enhancement above the similar, more detailed, curve obtained at greater geocentric distances. The latter curve is shown to be consistent with flux data obtained from recent lunar microcrater studies. The trend of increasing flux with decreasing geocentric distance is now positively established. The high flux which is detected at Prospero altitudes, a majority fraction of which appears to occur in clusters, a feature also apparent from HEOS data, is shown to be consistent with a model for the origin of near-Earth micrometeoroids based on the fragmentation of larger meteors in the upper atmosphere.