A comparison of channel-base currents and optical signals for rocket-triggered lightning strokes D. Wang a, T , N. Takagi a , T. Watanabe a , V.A. Rakov b , M.A. Uman b , K.J. Rambo b , M.V. Stapleton b a Gifu University, Japan b University of Florida, USA Received 30 October 2003; accepted 16 November 2004 Abstract A comparative analysis has been performed of the channel-base current and light waveforms for four rocket-triggered lightning strokes. It has been found that the current and light signals at the bottom of the channel exhibit a linear relationship (direct proportionality) in their rising portions. However, just after the peaks the linearity disappears, and the light signals usually decrease faster than the currents during the next several microseconds. Later, this trend is reversed and in some cases the light signals show another rising trend, even when the currents continue to decrease. The linear light/current relationship for the rising portions of the waveforms appears to be the same for different strokes. The findings support the idea of evaluating the variation of return stroke current along the lightning return stroke channel using light signals, provided that evaluation is limited to the rising portions of those signals and assuming that the light/current relationship observed at the bottom of the channel holds at other heights. D 2005 Elsevier B.V. All rights reserved. Keywords: Electrical discharge; Lightning; Return stroke; Electrical spark 0169-8095/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2004.11.025 T Corresponding author. Fax: +81 58 2301894. E-mail address: wang@cc.gifu-u.ac.jp (D. Wang). Atmospheric Research 76 (2005) 412 – 422 www.elsevier.com/locate/atmos