  The fine structure of micron-sized erosion spots within coaxial rings of
10-100 micron diameter, observed in the Mather type plasma focus, is analyzed.
The topological similarity of this structuring to that of electric current
filaments, observed in the Filippov type plasma foci and straight Z-pinches, is
shown. The possibility of interpreting this structuring in terms of the
formerly suggested hypothesis for long-lived electric current filament
formation, due to electrodynamic aggregation of nanodust in electric
discharges, is discussed.
