High-speed video and electric field observation of a negative upward leader connecting a downward positive leader in a positive cloud-to-ground flash

Marcelo M. F. Saba, Brazilian National Institute for Space Research - INPE, S. Jose dos Campos, SP, Brazil; and C. Schumann, T. A. Warner, J. Alves, J. H. Helsdon Jr., and R. E. Orville