Temperature of long sparks in air

A 6.4-MV impulse generator was used to create 15-ft sparks in air between a negative rod and a grounded plane. In the absence of breakdown the voltage applied to the spark gap was the standard 1. 5 × 40 wave. Spark current rose to a peak value of about 7, 000 A in about 5 usee and subsequently fell to half-value in about 5 μsec. Spectra (3, 900 to 8, 900 A) were recorded on film with 2-μsec time resolution.