Triangulation of red sprites observed above a mesoscale convective system in North China

The triangulation of red sprites was obtained, based on concurrent observations over a mesoscale convective system(MCS) in North China from two stations separated by about 450 km. In addition, broadband sferics from the sprite-producing lightning were measured at five ground stations, making it possible to locate and identify the individual causative lightning discharges for different elements in this dancing sprite event. The results of our analyses indicate that the sprites were produced above the trailing stratiform region of the MCS, and their parent strokes were located mainly in the peripheral area of the stratiform. The lateral offset between sprites and causative strokes ranges from a few km to more than 50 km. In a particularly bright sprite, with a distinct halo feature and streamers descending down to an altitude of approximately 48 km, the sprite current signal identified in the electric sferic, measured at a range of about 1,110 km, peaked at approximately 1 ms after the return stroke.

Discharge characteristics of leader inception and development under 10 m long air gap—experimental observation and simulation results

The physical mechanism of leader formation and development is not well understood.In this study,we present experimental and simulation results obtained with a 10 m long air gap discharge.A 10 m outdoor discharge experiment is carried out to obtain the current,voltage,and optical image during the leader discharge process.Four different impulse voltages were applied to the rod‐plane gap.The measured current is used as an input for a plasma model,then the temperature and electric field could be calculated.The simulation results show that the temperature of the streamer stem during the dark period may exceed 2000 K.In addition,the critical charge required for leader initiation can be as low as 0.27μC for a 10 m air gap.The channel temperature is relatively stable in the process of leader development,which is maintained at about 4500 K.The electron density is about 0.5–3�1020 m-3,and the discharge channel conductivity fluctuates in the range of 1–10 S/m for the leader current between 1 and 2 A.A long dark period is tended to be associated with a higher injected charge by the first streamer.It is inferred that the voltage increments during the dark period play an important role in promoting streamer‐to‐leader transition,except for temperature and the injected charge.