Current pulse shapes have been measured in negative and positive corona discharges mostly in dry air. Negative corona Trichel pulses and pulses corresponding to the primary streamer/cathode contact in a positive point-plane gap were found to exhibit remarkable similarities, indicating a positive-streamer-like mechanism for the Trichel pulse development. High-frequency instabilities of the high-pressure filamentary glow discharge, which can be responsible for the arcing from freshly polished cathodes, were observed and attributed to local positive-streamer-like breakdowns of the cathode sheath.

Current pulses of single and repetitive prebreakdown streamers have been measured in a positive point-plane gap in dry air at pressures of 3.33–26.7 kPa and at various overvoltages. The pulses of the single streamers exhibited a complex double-peaked form and, in contrast to the commonly held belief, differed significantly from those of the repetitive streamers. To explain the complex waveforms observed, a qualitative physical picture of the processes occurring during the streamer-cathode contact is outlined.