The after-effect of streamers of positive corona under combined voltage

The rise probabilities of positive corona streamers initiated by a flux of negative ions are investigated under the combined voltage (dc + ac) in point-to-coaxial cylinder discharge gaps in atmospheric air. A method is developed to detect and to estimate quantitatively an after-effect of the preceding streamer on the rise probability of the following one during the next cycle of the ac voltage. The method is based on the statistical analysis of sequences of streamers. The dependence of the intensity of the after-effect on de and ac voltage, ac frequency, pre-ionization level, air humidity and airflow velocity is investigated. The causes of the after-effect of streamers are discussed.