Evolution Characteristics of Electric Field for AC Corona Modes in Atmospheric Air

Electric field is one of the key parameters to study the charge dynamics for corona discharge. To study the motion characteristics of space charge in different corona modes of ac corona, electrooptic (EO) modulation technique was used to obtain the electric field in corona space. This article focuses on the time-varying characteristics of electric field for ac corona discharge modes. The step phenomenon is observed and the evolution characteristics of electric field for corona modes, from the Trichel pulses to the stable glow, are obtained. It was found that the background field could not remove the space charge generated by the discharge completely within half a cycle, which directly proved the existence of retained charge. And it is proposed that the continuous and fast rising electric field is the characteristic of positive glow in ac corona, which may be an effective method to judge the positive glow. Additionally, electric fields at different spatial locations were studied. The electric field step at the migration zone is suppressed, and as the space charge density increases, the suppression phenomenon becomes more obvious. This article provides more information on the physical mechanisms of the ac corona modes and gives support for the research of corona plasma.