Scaling laws in dc micro discharges*

In order to establish the operation regime of micro discharges we should start from the low pressure discharges and employ the standard scaling laws. Discharges should scale according to the reduced electric field $E/N$ and $p$d - product proportional to the number of collisions. Finally, the scaling should be made in accordance with the $jd^2 $ - describing the space charge effects [1]. We have calculated the Paschen curves and Volt- Ampere characteristic by using a PIC code and appropriate data for argon in order to establish whether the standard micro discharges operate in Townsend regime or in Glow Regime. \newline [1] A.V.Phelps, Z.Lj.Petrovi\'{c} and B.M.Jelenkovi\'{c}, Phys. Rev. E \textbf{47} 2825 (1993)