Lightning energetics: Estimates of energy dissipation in channels, channel radii, and channel‐heating risetimes

Abstract

In this report, several lightning‐channel parameters are calculated with the aid of an electrodynamic model of lightning. The electrodynamic model describes dart leaders and return strokes as electromagnetic waves that are guided along conducting lightning channels. According to the model, electrostatic energy is delivered to the channel by a leader, where it is stored around the outside of the channel; subsequently, the return stroke dissipates this locally stored energy. In this report this lightning‐energy‐flow scenario is developed further. Then the energy dissipated per unit length in lightning channels is calculated, where this quantity is now related to the linear charge density on the channel, not to the cloud‐to‐ground electrostatic potential difference. Energy conservation is then used to calculate the radii of lightning channels: their initial radii at the onset of return strokes and their final radii after the channels have pressure expanded. Finally, the risetimes for channel heating during return strokes are calculated by defining an energy‐storage radius around the channel and by estimating the radial velocity of energy flow toward the channel during a return stroke. In three appendices, values for the linear charge densities on lightning channels are calculated, estimates of the total length of branch channels are obtained, and values for the cloud‐to‐ground electrostatic potential difference are estimated.