LF/VLF and VHF lightning fast-stepped leader observations

[1] This paper reports multiplatform observations of leader radiation preceding initial cloud-to-ground lightning return strokes by <6 ms. Specifically, we present multistation ground-based LF/VLF recordings of events with large-amplitude leader activity (comparable in amplitude to the return stroke amplitude). The events were selected for their coincidence with VHF observations by the FORTE satellite. Some FORTE VHF leader step observations have obvious direct and ground reflection components. For these steps, which temporally correspond to specific features in the ground LF/VLF field change records, we calculate a source height based on event satellite geometry. We determine source heights between 4.0 and 5.5 km. For FORTE records with multiple reflected events we calculate vertical leader propagation velocities on the order of 10 6 m/s. The determined vertical leader propagation speeds are an order of magnitude greater than those reported as typical values for stepped leader velocities associated with initial return strokes.