Microsecond-scale Electric Field Pulses in Cloud Lightning Flashes

From wideband electric field records acquired using a 12-bit digitizing system with a 500-ns sampling interval, microsecond-scale pulses in different stages of cloud flashes in Florida and New Mexico are analyzed. The pulse occurrence statistics and waveshape characteristics are presented, The larger pulses tend to occur early in the flash and presumably are related to the flashinitiating breakdown processes. This result contradicts the common view found in the atmospheric VLF radio noise literature (e.g., [l]) that the main sources of electromagnetic radiation in cloud flashes are K processes which occur in the final, or J-type, part of the cloud flash.