Production of Ball-Lightning-Like Luminous Balls by Electrical Discharges in Silicon

We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.

Figure 1

(a) Experimental arrangement showing the power supply, electrode geometry and the Si wafer. (b) The top electrode is lowered until it touches the Si piece and closes the circuit. (c) The top electrode is raised up to a distance of 1 to 2 mm, approximately. An electrical arc is formed during this upraising movement. Hot-glowing fragments and, eventually, ball-lightning-like luminous balls fly away in all directions.

Figure 2

Successive video frames showing the luminous balls bouncing off the ground. Time interval between the frames is 80 ms. See also the supplementary video 2 [19].

Figure 3

Successive video frames showing a luminous ball passing through a small gap under an electrical conductor. Time interval between the frames is 80 ms. See also the supplementary video 3 [19].

Figure 4

Successive video frames showing a luminous ball leaving spiraling smoke trails above it. Time interval between the frames is 80 ms. See also supplementary video 4 [19].

Figure 5

SEM of the Si wafer before (a) and after electrical discharge (b),(c),(d). The surface of the samples subjected to electrical discharges shows holes (b),(c) and chains of micrometer-sized particles (d).