Abstract
An expression of the velocity of the streamer advance along a previously ionized channel in the lightning discharge is obtained on the basis of an equation which represents the time variation of the electron density in a channel. The expression shows that, as the electron density in a previously ionized channel tends to zero, the velocity of the streamer tends, as expected, to that of the streamer advance through the virgin air (i.e. of the pilot streamer). The numerical evaluation for the velocity is obtained by the graphical method in the case of the stepped streamer, where the reasonable model of the tip field of the streamer is assumed. The result shows that the velocity of the streamer thus calculated agrees fairly well with the observed value of the velocity of the stepped streamer in the lightning discharge.
