Narrow bipolar pulse
Narrow bipolar pulses are high-energy, high-altitude, intra-cloud electrical discharges associated with thunderstorms. NBP are similar to other forms of lightning such as return strokes and K-changes, but produce an optical emission of at least an order of magnitude smaller. They typically occur in the 10–20 km altitude range and can emit a power on the order of a few hundred gigawatts. They produce far-field asymmetric bipolar electric field change signatures (called narrow bipolar events).
References
[1] M.A. Uman et al., The Electromagnetic Radiation from a Finite Antenna, AJP Vol. 43, 1975.
[2] A.V. Gurevich, K.P. Zybin, Runaway Breakdown and the Mysteries of Lightning, Physics Today 37-43, 2005.
[3] K. B. Eack, Electrical characteristics of narrow bipolar events, Geophysical Research Letters, Vol. 31, 2004.
[4] R. Thottappillil, Distribution of charge along the lightning channel: Relation to remote electric and magnetic fields and to return-stroke models, Journal of Geophysical Research, Vol. 102, 1997.