Visible channel development during the initial breakdown of a natural negative cloud-to-ground flash

Author(s)

Campos, Leandro Z. S. ^[1] ; Saba, Marcelo M. F. ^[1]

Affiliation

^[1] Natl Inst Space Res, ELAT CCST, Sao Paulo - Brazil

• Document type: Journal article
• Source: Geophysical Research Letters; v. 40, n. 17, p. 4756-4761, SEP 16 2013.
• Web of Science Citations: 17

Abstract

GPS time synchronized high-speed video records (at 4000 frames per second) and electric field waveforms are discussed for one stepped leader of a negative cloud-to-ground flash whose initial development becomes visible above cloud base. The leader emerges from the opaque region of the thundercloud around 4800 m above ground, propagating with speeds of the order of 10(6) m s(-1). It is possible to see that this early, bright, and fast propagation period occurred simultaneously with the emission of initial breakdown bipolar pulse trains. The leader gradually reduces its speed and luminous intensity: When its tip is less than 3000 m above the ground, the propagation speeds oscillate between 2 and 4x10(5) m s(-1) until it makes contact approximately 16 ms after it first became visible. With time, the initial breakdown waveform is gradually replaced by unipolar pulses and the leader propagation speed drops to the 10(5) m s(-1) range. (AU)

• FAPESP's process: 10/02716-5 - Characterization of M components and leaders of natural lightning from high-speed video observations and atmospheric electric field measurements
• Grantee: Leandro Zanella de Souza Campos
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 03/08655-4 - Brazilian Program to Monitor Lightning
• Grantee: Osmar Pinto Junior
• Support Opportunities: Research Projects - Thematic Grants