The return stroke current attenuation function: Available models and identification methods from field measurements

The paper presents the state of the art of the available models to represent the lightning return stroke channel current. In particular, attention is paid to the engineering models and to the function that expresses the attenuation of the current while flowing in the discharge channel. Two strategies have been developed in literature: the first one proposes some functions and validates them by means of comparisons between the electromagnetic fields calculated starting from the assigned model and the measured ones. Another possibility consists of measuring the electromagnetic field and reconstructing the channel current by solving an inverse problem, which can be done resorting to some dedicated mathematical tools: the so-called regularization techniques.