The optical characteristics of surface dielectric barrier plasma actuators with a wire/planar electrode combination and 1 kHz triangular applied voltages were studied using an intensified charge-coupled device camera and a monochromator in atmospheric pressure air. The spatial and temporal images were recorded both parallel and perpendicular to the aerodynamic actuator surfaces on nanosecond time scales. Arc-shaped discharges jumping from above the powered wire across the dielectric above the grounded planar electrode were observed for the first time. Nitrogen molecular second and first positive band lines were observed and the discharge temperatures were calculated by matching the experimental spectra with SPECAIR lines (Laux et al 2003 Plasma Sources Sci. Technol. 12 125-138). The electron temperatures were found to be 6800 +/- 400K from the SPECAIR code.