Lichtenberg Figures

patterns of distribution of spark channels that cover the surface of a solid dielectric in cases of creeping spark discharge. It was first observed in 1777 by G. C. Lichtenberg.

In a strong discharge, the high pressures and temperatures in the spark channels deform the surface of the dielectric and imprint Lichtenberg figures. In weak discharges the Lichtenberg figures correspond to selective polarization of the dielectric and can be made visible by sprinkling a special powder on the surface of the dielectric or by developing a photographic plate placed under a layer of the dielectric during the discharge. The Lichtenberg figures near the anode and cathode sharply differ in appearance; therefore, they may be used to determine the electrode from which the spark channels developed (the polarity of the spark discharge). Lichtenberg figures are used in special devices for determining the polarity and force of lightning discharges.