A simple physical model for self-triggered upward leaders from high-rise buildings

This paper presents a simple physical model for an upward positive leader initiated from a tall grounded object. Characteristics such as the leader channel structure, leader initiation criteria, leaded propagation speed, leader current and channel longitudinal electric field are described and modelled step-by-step. Other parameters including the evolution of leader line charge density, leader core conductance and radius, and leader corona sheath radius are also computed and evaluated. Particularly, the minimum corona sheath radius and corona charge density for leader initiation and stable propagation based on existing experiment data are proposed. The model may serve as a virtual lab to study the initiation of an upward leader at the top of a tall ground structure for tall building lightning protection analysis.