A class of analytical functions to study the lightning effects associated with the current front

The lightning currents are measured on tall structures and by artificially initiated lightning. Additionally they are deduced from the remote electric or magnetic field radiated during the so-called return stroke phase, when the lightning current is flowing to earth. For this purpose return stroke models were developed giving the dependency between the field data and the current along the ionized return stroke channel. The most frequently employed models use the so-called channel-base currents, which are commonly expressed by analytical functions to simplify the calculation procedure. A review is given about a class of analytical functions being very convenient in such calculations. The special attention is given to the type of current function most frequently used in lightning research and standardization. With these functions the fine structure in the current front can be studied, which is of basic interest with respect to the lightning protection.