Time and Directional Study of Primary Heavy Nuclei

The "plate mover" technique has been used in two emulsion studies of the time dependence of the flux of primary heavy nuclei ($Z\ge 10$). No evidence for the previously reported "day-night" effect was found. The angular distribution was studied on an oriented flight, and some statistically significant azimuthal asymmetries were noted, but these showed no obvious trend in time. The absorption mean free path was found to be 19 g/${\mathrm{cm}}^2$, independent of depth in the atmosphere for depths ≥18.5 g/${\mathrm{cm}}^2$.