Comparison of lightning and a long laboratory spark

Long laboratory sparks are often considered to be miniature lightning. The salient properties of 4-m sparks created by impulse breakdown between a negative rod and a grounded plane by the Westinghouse Trafford 6.4 MV impulse generator are compared with those properties of natural lightning. In particular, a comparison is made of the luminous processes associated with breakdown, the current, voltage, power, and energy inputs to the discharges, the radiated visible spectra, the temperature, electron density, and pressure in the discharge channels, the absolute broad-band radiation in the visible and near infrared wavelength range, and the radiated acoustic signals. The spark return stroke most resembles a weak subsequent stroke in a multiple stroke lightning flash. The leader processes of the spark differ considerably from those of lightning.