The influence of the breakdown electric field in the lightning corona sheath on the dynamics of the return stroke

A generalized lightning traveling current source (GTCS) return stroke model has been used to examine the characteristics of the lightning channel corona sheath surrounding a thin channel core. The return stroke process is modeled with positive charge coming from the channel core discharging negative leader charge in the corona sheath. The corona sheath model that predicts charge motion in the sheath is used to derive sheath radius vs. time expressions during the return stroke. According to the corona sheath model, previously proposed by Maslowski and Rakov [2006] and Maslowski et al. [2009], it consists of two zones, zone 1 (surrounding the channel core with net positive charge) and zone 2 (surrounding zone 1 with negative charge). We adopted the assumption of a constant electric field inside zone 1 of the corona sheath observed in laboratory experimental research of corona discharges. We examined the influence of different magnitudes of the breakdown electric field at the boundaries of both zones on the dynamics of the return stroke. This approach can be viewed as a generalization of the corona sheath model given in the previous study by Cvetic et al. [2011]. The calculations have shown that the radii of zones 1 and 2 decrease with the increase of the breakdown electric field in the corresponding zone. Similar conclusion holds for the velocities of zone 1 and 2 boundaries. However, their velocities are much lower (about three orders of magnitude) than the return stroke velocity, Tausanovic et al. [2010]. Simultaneously, a slight decrease of zero crossing time of the velocity of zone 1 boundary, as well as a decrease of the quotient of maximum radii of both zones are observed.